Four days in San José: look into a live crater and be back for lunch

Start beneath the main square, where the Museo del Oro Precolombino occupies three underground floors. There are about sixteen hundred pieces in it, made between roughly 500 and 1500 AD, most of them from chiefly burials on the southern Pacific slope: frogs, eagles, crocodiles, shamans mid-transformation, and a great many small figures whose function nobody agrees on. The museum is good on how the goldwork was made, which is where lost-wax casting turns out to be the interesting part.

Come up into daylight and go into the National Theatre next door. It was paid for by a tax the coffee exporters agreed to put on their own coffee, after the country was left off a touring soprano's itinerary for want of a stage worth singing on, and it opened in 1897. Inside are marble stairs, gilt, a ceiling painting of coffee and banana harvesting that used to be on the five-colón note, and a café in the foyer. Tours run several times a day and take under an hour.

Then walk it off. Avenida Central is pedestrianised and loud, the central market a couple of blocks west is a warren of stalls and sodas where a plate of the day costs a few dollars, and Parque Morazán at the eastern end is where the city sits in the evening. On Thursdays a crowd of jugglers takes over one corner of it with drums.

Leave early. Irazú is the highest volcano in Costa Rica and the summit is above the tree line, a grey lunar plain of ash and scoria with a green-blue crater lake in the main pit, and on a clear morning you can supposedly see both oceans from the top. The catch is that it clouds in almost every day by mid-morning, so a seven o'clock departure is the difference between a view and a white wall. It last erupted seriously in 1963, on the day President Kennedy arrived in the country, and covered San José in ash for months.

Come down to Cartago, which was the capital of Costa Rica until the 1820s and lost the title to San José. In the middle of its main square stand the ruins of the parish church of Santiago Apóstol, rebuilt repeatedly through the colonial period, wrecked again by the earthquake of 1910 and never finished. What is left is a roofless stone shell with a garden inside it, mostly locked, and the walls are the best colonial masonry in the country.

Four blocks east is the Basílica de Nuestra Señora de los Ángeles, which is the religious centre of Costa Rica. The story is that in 1635 an indigenous girl found a small black stone figure of the Virgin on this spot, took it home, and found it back on the rock the next morning, repeatedly, until a church was built where she found it. La Negrita is about eight centimetres tall and sits above the altar; the rock and its spring are in the crypt below. On 2 August hundreds of thousands of people walk here overnight from San José and beyond, on foot, along the main road.

Poás needs planning and rewards it. Entry is by timed slot booked online in advance, numbers are capped, and visitors are kept to a viewing platform for a limited period, because this is a genuinely active volcano that has closed the park more than once. From the platform you look straight down into a crater more than a kilometre across, with a grey acid lake at the bottom and steam coming off it, and the smell of sulphur is unmistakable. Book the earliest entry you can get: the crater is usually clear at seven and hidden by ten.

A short path off the same car park runs through stunted, wind-bent cloud forest to Botos, a cold blue-green lake filling an older crater that has been quiet for thousands of years. It is a twenty-minute walk each way and almost nobody does it, which after the queue at the viewpoint is a relief.

On the road back down, La Paz Waterfall Gardens is the obvious afternoon. Trails run down a steep river gorge past five waterfalls on walkways and steps, and the same ticket covers a large walk-through hummingbird gallery, a butterfly house, a serpentarium and enclosures of rescued wildcats and monkeys. It is expensive by Costa Rican standards and it is the closest thing to a whole country's wildlife in one afternoon.

The Museo del Jade holds more pre-Columbian jade than anywhere else in the Americas, and since its move into a purpose-built block off the Plaza de la Democracia it has been one of the best-presented museums in Central America. Five floors take you through jade as material, as status object and as burial goods, with the pendants lit from behind so you can see through them. Costa Rica's jade is mostly a green stone traded from a long way north, which is part of what the museum is about.

Then walk two blocks to the Museo Nacional, which occupies the Cuartel Bellavista, a yellow fortress above the Plaza de la Democracia. On 1 December 1948, standing here, José Figueres took a sledgehammer to the wall and abolished the Costa Rican army, which is why the country has had none since. The pockmarks of the civil war earlier that year are still in the outside walls, and you walk in through them.

Inside are the stone spheres from the Diquís delta on the Pacific coast, near-perfect granite globes up to two metres across that were made between roughly 300 and 1500 AD and whose purpose nobody has established. There are also colonial rooms, a walk-through butterfly enclosure and a terrace with the whole city in front of it. Then the airport, half an hour away when the road is clear and an hour when it is not.