Three days in Turku: Finland's oldest city, demoted and much improved by it

Turku Cathedral was consecrated in 1300 and it is the national shrine of Finland, mother church of the Finnish Lutherans and, by common agreement, the most important building in the country. It is brick, it has been burnt and rebuilt repeatedly, most drastically after 1827, and the side chapels hold bishops, generals and one queen: Karin Månsdotter, a soldier's daughter who married Erik XIV of Sweden and ended up living out her life on a Finnish estate. The bells are broadcast at noon across the whole of Finland, and on Christmas Eve they are what the country listens to.

The Old Great Square, three minutes downhill, was the centre of Turku from the thirteenth century until the fire, and the four restored mansions around it are what a merchant town looked like before the grid. The Brinkkala balcony is where the Christmas peace is read.

Then go under the ground. Aboa Vetus is an archaeological site that was found by accident in 1992 when a shipping magnate's house was being converted into an art gallery, and the excavation turned up a whole block of the medieval town: cellars, streets, a well, the foundations of houses that were buried when the city was levelled and rebuilt. You walk on the medieval street level, several metres below the present one. The same ticket includes Ars Nova upstairs, the contemporary art half, and the contrast is the point of the place.

Luostarinmäki is what Turku looked like before 1827. It was the poor quarter on the hill, wooden, cramped and outside the town proper, and it was the only substantial part of the city the fire did not reach. Rather than clear it, the city preserved it, and it is now a handicrafts museum where over thirty workshops stand on their original sites, which is rare almost to the point of being unique among open air museums: nothing here was moved in from somewhere else. In summer there are craftsmen working in them, a post office and a café.

Then walk downstream. The riverside path runs three kilometres from the town to the sea, past the boats and the bridges and the free ninety second ferry, and it is flat the whole way.

Forum Marinum sits on the west bank near the bottom. Inside it is the national maritime museum and the Finnish navy museum; outside, moored in the river, are the ships, which are the reason to come. Suomen Joutsen is a full rigged three master built in France in 1902 that served as a training ship; Sigyn is a wooden barque from 1887, the last of her kind afloat. There are minelayers, a corvette and assorted small craft. The ships open in summer only, the exhibitions all year.

Turku Castle is five minutes further, at the mouth of the river beside the Stockholm ferry terminal. Building began in the 1280s and it grew for three centuries into the largest castle in Finland, a grey stone block with a Renaissance floor added by the dukes who held it. It has been a fortress, a royal residence, a granary, a prison and a bombing target, and the two tours through it, one medieval and one sixteenth century, take a couple of hours between them. The staircases are steep and narrow and there are very few short cuts, which is worth knowing before you start.

The Turku Art Museum sits at the top of Aurakatu in a granite National Romantic building of 1904, which is itself part of the visit: heavy, rough cut stone with carved details, the Finnish answer to Art Nouveau. The collection is Nordic and its strength is the golden age around 1900, the generation who were inventing a Finnish visual identity at the same moment as Sibelius was doing it in music. There is also Finnish surrealism, which is stranger and better than it sounds.

It is four hundred metres from the market square and about fifteen minutes from the station, so it works whatever time the train goes.