Escape the heat or rain underground!
A labyrinth of caves and tunnels span for miles under Castle Hill, about two hundred known caves and you can visit four of the most extensive and spectacular ones. Formed by thermal actions and many centuries of human activity, (most recently used as an air-raid shelter during World War II, with room for thens of thousands of people!). Labyrinth of Buda Castle is our favourite, stretching for over six very humid miles beneath the streets and buildings of the ancient Castle District of Buda. The aged walls and arches really are something amazing to behold.
– Budavári Labirintus, I District: Úri utca 9, www.labirintus.com