A cave walking tour in Budapest, under the castle and beyond

Castle Hill looks solid from the river, but a cave walking tour in Budapest shows you how much of it is empty. The tourism agency describes the rock under the district as full of caves, tunnels and cellars, some of them medieval.⁹ Over the centuries people widened natural hollows into storerooms, escape routes and shelters, so the underground world mixes geology with human history at every turn.

Some of those uses sound unlikely now. The National Bank of Hungary once kept the country's gold reserves in a storage area cut into the hill.¹⁰ Systematic exploration only began in the 1930s, led by researcher Ottokár Kadič, which is why surprises still turn up and why guides keep finding new stories to tell.¹¹ The national park that runs the official cave tour describes the system as 3.3 km long under the castle.¹

You have a choice of visits. Under the castle itself, the national park leads guided walks through the cave system, and a separate museum occupies the wartime hospital cut into the rock. Out in the Buda Hills, a pair of show caves with real dripstones and crystals take you into natural passages formed by warm water. Each has its own rules on age, fitness and photography, so read the details before you book.

Many visitors arrive asking for the Labyrinth, and the name covers a real history. In the Middle Ages servants and soldiers used the tunnels to move about without disturbing the nobles living above them.³⁷ During the Cold War, in the 1950s, a section of the passages became a hidden refuge, sealed by heavy doors and supplied with fresh air.¹⁴ It has still not been fully mapped, and bricked-up passages keep surfacing during building work.³⁸

Only some of the tunnels are open to the public, and the tourism agency says so plainly.³⁹ That is worth knowing before you follow a sign or a street hawker: the visit you book should state which part of the system you enter and who runs it. The national park tour described above and the hospital museum below are the official ways into the rock under the district, and both publish their rules openly. If a ticket seller cannot tell you the operator, walk on.

Above ground, the stories carry on. The district's ghost tales, collected by writer Gyula Krúdy, include kings who leave the walls at night.⁴⁰ Guides often weave such legends into a cave visit, which suits children who find dates heavy going. Combine the cave with a walk on the plateau and you see both halves of the hill in an afternoon, the palace above and the cellars beneath it.

Most famous caves were carved by cold rainwater seeping down through limestone. Several Buda caves tell a different story. The national park explains that the Szemlő-hegyi Cave was formed by thermal water rising from below, which left unusual crusts that look like popcorn and growths shaped like cauliflower.⁹³ That warm-water origin is what makes the Buda Hills caves interesting to geologists and to curious families.

The Pál-völgyi Cave shows the same hand at work. The tourism agency lists its narrow, gap-like corridors, big changes in level, scallops cut by hot water and handsome stalactites.³⁵ Its known passages run to almost 32 kilometres, though only a small part is shown to visitors.⁹⁴ The Szemlő-hegyi Cave is nicknamed the underground flower garden of Budapest for its mineral formations.⁹⁵ Seeing both shows how differently warm water can work the same rock.

The same hot springs explain a pleasant surprise on Gellért Hill. The Cave Church in the rock there stays at around 20 degrees Celsius all year, because the warm springs run through the hill.²⁸ The cave tours are cooler: VisitHungary puts the general cave temperature near 10 degrees Celsius, and the national park measures 11 °C in Pál-völgyi and 12 °C in Szemlő-hegyi.^96,26,27 Whichever you choose, the change from the street is noticeable within minutes.

Temperature is the first thing to plan for. Even in high summer the castle cave sits at 12 °C and Pál-völgyi at 11 °C, so a fleece or light jacket makes the walk far more pleasant, and a scarf helps anyone who feels the cold.^4,26 Floors are paved in the castle cave but uneven and stepped in Pál-völgyi, so wear closed shoes with grip.^22,81 A small torch is not needed on the lit routes, though it makes reading signs easier.

Age rules differ by site and are strictly applied. The Hospital in the Rock does not admit children under 6 because the exhibition is disturbing, and it does not recommend a visit under 12 without a parent's approval and supervision.^33,110 The castle cave suggests age 12 for its longer route and 5 for the short one.^23,24 Pál-völgyi sets a minimum height as well as an age.³⁰ Bring a document for older children if they look young for the rule.

If confined spaces worry you, start with Szemlő-hegyi, which is step-free, or the short castle route of about 45 minutes.^36,3 Pál-völgyi's ladder and narrow sections suit confident walkers best, and nervous visitors can always wait above.⁸¹ For a guided taste of the real thing, the adventure caving trip sends small parties of no more than 10 crawling for 3 hours. Book it only if everyone in your group is happy on hands and knees.