Budapest is home to a network of historical and hidden bunkers, ranging from wartime hospitals to Cold War nuclear shelters, offering a glimpse into the city's layered past.

The Hospital in the Rock (Sziklakórház), located beneath Castle Hill, is a former underground hospital used during World War II, particularly during the Siege of Budapest, and later converted into a Cold War-era nuclear bunker.
It is accessible only on guided tours that run hourly in both English and Hungarian, taking visitors through tunnels into the old hospital and ending in a radiation contamination room where an air-raid siren can be activated.
The site features wax figures depicting wartime conditions and is a major tourist attraction.

Another significant site is the F-4 Object, also known as the Rákosi Bunker, a secret nuclear shelter built beneath the city center between Kossuth tér and Szabadság tér.
Constructed between 1949 and 1953, it was designed to shelter Mátyás Rákosi and the Central Committee of the Hungarian Working People’s Party in the event of a nuclear attack.
The bunker, located 39 to 50 meters below the surface and shaped like an "H", has a direct connection to Line 2 of the Budapest Metro and reportedly a tunnel to the Hungarian Parliament Building.
Despite its completion, it was never used for its intended purpose and remains closed to the public, though its emergency exit can be found near Szabadság tér.

The Citadel Bunker, located on a hill in the old town, was originally used by the Luftwaffe during World War II and later transformed into a war museum.
It provides insight into the Second World War in Budapest, with a focus on the siege of the city.

Additionally, the Labyrinth beneath Castle Hill is a natural cave system with a history spanning prehistoric times to the 12th century, used as wine cellars, mines, and even rumored to have housed Vlad the Impaler.
It is now a tourist attraction featuring wax figures and a spooky, lantern-lit experience after 6 p.m.