Twelve days in Slovenia and Croatia: green water first, blue water after

Start where the town does, at the crossing where the road from the old market met the road out of the medieval walls. The middle span dates from 1842 and became a bottleneck, so in the early 1930s Plecnik added a footbridge on either side and fanned them out, turning a traffic problem into a small stone piazza over the water.

The cathedral is a minute east. It went up between 1701 and 1706 with ceiling frescoes by Giulio Quaglio, but the thing to look at is outside: two bronze doors added in the 1990s, one showing a thousand years of Slovene Christianity, the other six bishops of Ljubljana, cast in a heavy expressionist relief that people run their hands over until it shines.

Then up the hill. The funicular takes a minute from the market end and the walking path takes twenty, and the reward at the top is the outlook tower: the whole basin, the Sava beyond it and the Kamnik Alps closing the view to the north. There has been a fort up here since the twelfth century, though most of what stands is fifteenth and sixteenth century rebuilding after an earthquake, and the nineteenth century tower was put up as a fire watch.

Come down for dinner in the old town. This is the cheap end of the trip and Slovenian food is heavier than anything on the coast, so make the most of it.

The market is a morning affair and dies by two, so go early. Plecnik built the curving riverside colonnade for it between 1940 and 1942, a double-storey arcade with fish sold in the vaults underneath and a covered walk along the top, and it is the best single thing he made in the city.

The National Gallery holds the Slovene canon, which is worth an hour even if the names mean nothing to you: the impressionists of the 1900s painting the same alpine light everybody comes here for. It also holds the original of the Robba fountain, moved indoors in 2008 and replaced outside by a copy, so the eighteenth century marble is now in a glass hall rather than the weather.

Spend the afternoon at the far end of the day's walk, in the small round house where Plecnik lived from 1921 until he died in 1957. It is kept as he left it, down to the furniture he designed and the drawings on the table, and a guide takes you round in small groups. It explains the rest of the city better than any museum could.

Nothing else needs doing. Ljubljana is a town for sitting in.

The bus leaves early and takes most of the morning, with a change in Zagreb and a border crossing that is now an internal Schengen one but can still slow things down in August. Take food with you; the stop is not long enough to eat properly.

Get off at park entrance 1, which is the lower end of the canyon and the right way to see it first. The path drops in switchbacks from the road and the whole lower system opens up below you in one view, which is the photograph everybody has seen and it is better in person.

At the bottom is the Great Waterfall, where the Plitvica stream comes off the cliff in a single drop of about seventy-eight metres, the tallest in Croatia. The boardwalk runs right under the spray. From there the path threads back up past a string of small lakes, each held in by a wall of travertine that the water is still slowly building.

Halfway up, a staircase cut into the rock climbs through a cave to the canyon rim. It is short, dark and slippery, and it is worth it for the view back down. The West German Winnetou films were shot in these woods in the 1960s, which is why half the visitors are German and know the place by heart.

Late afternoon is the good hour here. The coaches have gone and the light comes down the canyon rather than into it.

Be at the gate for the first entry slot. The boardwalks are barely wider than one person, so an hour's head start is worth more here than at any other stop on this trip.

The day starts with the electric boat across the big lake in the middle of the park, the largest of the sixteen and the only one deep enough to be dark. The crossing takes about fifteen minutes and is included in the entry ticket. On the far shore, a wooded peninsula carries the ruins of a small medieval fort, which is the only human structure in the park older than the boardwalks.

Above the boat pier the upper lakes begin, and they are the prettier half: wider, shallower, with the barriers between them low enough to walk beside. The paths criss-cross the water on planks laid straight across the falls, and in places you are standing on the dam itself with the lake at your ankles.

Keep going to the top pool, the highest and second largest of the chain, where the canyon opens out into forest and the crowds thin to nothing. Shuttle buses run from the road above it back down to the entrances, so there is no need to walk the whole thing twice.

The bus down to the coast takes about two and a half hours and the last of it is the good part, dropping off the Velebit escarpment with the sea and the offshore islands laid out flat below.

Zadar's old town is a peninsula you can cross in a quarter of an hour. Its Roman forum is unusually exposed, because Allied bombing in 1943 and 1944 destroyed most of the buildings that had grown over it, and what was left was cleared rather than rebuilt. Column stumps, paving and a pillar of shame stand in an open square where people now sit with a coffee.

The round church beside it went up in the ninth century, straight on top of the forum, using Roman stone with the carved faces turned inwards where nobody would see them. Look at the floor and the base of the walls and the borrowed material is obvious. It has not been a working church since 1797 and is used for concerts, because the acoustics under the dome are extraordinary.

Then the waterfront for sunset, which is the reason people stay a night. Thirty-five sets of organ pipes are built under the marble steps at the tip of the peninsula, tuned to chords and played by the swell, so the sea makes a slow shifting drone that changes with the weather. It was finished in 2005 and it is the best public artwork on this coast.

The cathedral is the largest Romanesque church in Dalmatia, begun in the twelfth century and finished in the thirteenth, with a blind-arcaded front that repays five minutes of standing still. Its bell tower is a much later addition, designed by the English architect Thomas Graham Jackson and completed in 1892, and the climb is the only high view over the peninsula.

Ten minutes away is a museum that sounds dull and is not: Roman glass, thousands of pieces of it, dug out of the graves around the city where Zadar was one of the empire's glassblowing centres. Perfume bottles the size of a thumb, all of them iridescent from eighteen hundred years underground. There is a working furnace downstairs and the demonstrations run through the day.

That is enough sightseeing. The peninsula is small, the cafes are cheap and there is a swimming platform on the north shore ten minutes from the forum.

Come back to the waterfront after dark for the second half of the pair. A circle of glass plates twenty-two metres across is set flush into the quay, wired to solar cells underneath, and after sunset it runs through a slow light sequence while the organ keeps playing beside it. Children treat it as a dance floor and nobody minds.

Two hours down the motorway and you are in the biggest city on the coast. Split's bus station, railway station and ferry terminal sit in a row on the harbour, five minutes' walk from the palace gate, which makes arriving here easier than anywhere else on this route.

Walk in through the southern wall, straight off the seafront, and the first thing you reach is the palace basement: a set of vaulted halls that held nothing but rubbish for centuries and therefore preserved the exact floor plan of the emperor's apartments above. Climb the stairs at the far end and you come out into the courtyard.

This is the centre of the whole thing, a sunken square with granite columns down both sides shipped in from Egypt, sphinxes at the corners that were already ancient when Diocletian shipped them over, and the mausoleum on the east side. People have been standing about in it since 305. There is a cafe on the steps where you sit on cushions on the stone.

Late afternoon, walk out through the eastern gate to the market. It is the real one, feeding the city rather than the visitors, and it winds down around six.

Be at the cathedral when it opens. It was built as Diocletian's mausoleum, an octagon inside a ring of columns, and turned into a church around the seventh century by the people whose faith he had spent his reign persecuting. It is dedicated to a bishop he had put to death in 304, and the emperor's own sarcophagus vanished long ago. It is one of the oldest buildings anywhere still working as a cathedral.

The bell tower is a separate ticket and a separate climb, up open-sided stairs with the drop visible the whole way. It went up in the thirteenth century, was taken apart and rebuilt between 1890 and 1908, and the platform at the top gives you the palace roofs, the harbour and the islands stacked up behind them.

Across the narrow lane on the west side of the courtyard is the best preserved Roman room in the complex, a small temple with its original coffered barrel vault, later used as the baptistery. A headless sphinx guards the door. Ten minutes, and the vault is the point.

Then stop. The afternoon is for the sea. Split's swimming beach is a fifteen minute walk east of the palace and shallow enough to walk out fifty metres, which is why the local ball game was invented there.

Walk west out of the palace and up the slope of the wooded hill that closes the town. Twenty minutes along the shore road is the villa Ivan Mestrovic built for himself in the 1930s, with formal gardens above the sea and the largest collection of his work anywhere. He left Yugoslavia in 1942, gave the house and its contents to the state in 1952 and never came back.

The ticket also covers a small chapel two hundred metres further on, a converted sixteenth century house where he carved a cycle of walnut panels of the life of Christ over most of thirty years. Most visitors miss it and it is the better half.

In the afternoon, the archaeological museum twenty minutes north of the old town. It opened in 1820, which makes it the oldest museum in the country, and it holds what was carried in from Salona, the Roman provincial capital a few kilometres inland that Split's founders were running away from. The courtyard is lined with sarcophagi and gravestones and is free to walk into.

The rest of the day belongs to the hill. Paths run up through the pines to a lookout above the palace, and there are two small swimming coves on the far side with almost nobody on them.

The fast boat leaves the harbour early and takes about four and a half hours, threading between the islands and calling at Hvar and Korcula on the way. It carries foot passengers only, seats are numbered and August sailings sell out, so this is one ticket worth buying weeks ahead. Sit outside if you can stand the wind.

Dubrovnik's ferry berth is at Gruz, twenty minutes by bus from the old town. Go straight to the western gate: a stone bridge over a dry moat, a drawbridge that was raised every night for four centuries, and then a sudden drop down steps into the main street.

That street is one straight limestone canyon polished to a shine, laid out after the earthquake of 1667 flattened almost everything. At the near end stands a domed fountain of 1438, the outlet of an aqueduct that brought water twelve kilometres from a spring inland and made a siege survivable. Sixteen taps, still running, and everyone fills their bottle.

Then eat, walk the side lanes, and go to bed early, because tomorrow starts at eight.

The walls open at eight and everything about this day depends on being there. The circuit is about two kilometres, up to twenty-five metres high and six thick on the landward side, and it takes an hour and a half at a walking pace with stops. By eleven it is a single-file queue in full sun with no shade and no way to turn back. At eight it is empty and the roofs are still in shadow.

The same ticket gets you into the fort on the rock outside the western wall, which was built to stop an attack from the sea and from the town itself: the walls facing the city were left deliberately thin so the garrison could never turn on the republic. Over the gate is the line about liberty not being sold for all the gold in the world. It is a steep set of steps and a very good view back at the walls you have just walked.

After lunch, the palace where the government sat. The rector who ran the republic was elected for one month at a time and could not leave the building during his term, which tells you most of what you need to know about how the place stayed independent for five centuries. Inside is the city museum, with the state coach, the courtroom and a courtyard used for concerts in summer.

Fifty metres away is the one grand building that came through the 1667 earthquake intact, a Gothic and Renaissance palace that has been a customs house, a mint, a bank and a school. It now holds the state archive, and one room inside is a memorial to the defenders of the city killed in the war of the 1990s.

Two things before the airport bus, both a minute from the main street and both taking under an hour.

The Franciscan monastery just inside the western gate has a Romanesque cloister with sixty carved double columns, no two capitals alike, and a pharmacy that has been dispensing since 1317. It is one of the oldest still operating in Europe and it still sells hand creams over a counter at the front, with the old jars and the manuscripts in the room behind.

The other is a small gallery of conflict photography, opened in the early 2000s, with exhibitions that change through the season. It is unsentimental and hard going and it is the only place in the old town that says anything direct about what happened here in 1991 and 1992, when the city was shelled for seven months.

The airport is twenty kilometres south and the shuttle leaves from the bus station at Gruz and from the cable car stop above the Pile gate. Allow an hour more than you think in summer, because the coast road backs up.