Thorough exploration of these tunnels only started in the 1930s under supervision of specialist researcher Ottokár Kadič. Accordingly, they are sure to hold many more secrets even to this day. Some parts of the labyrinth these tunnels compose are open to the public.
Smart thinking saw the cavernous inside of the hill utilized as a hospital in World War II. The treatment rooms were set up in existing caves and crevices and hold the memory of many troubled times for Budapest. The hospital provided treatment to hundreds of soldiers but also served as a shelter when the castle was under siege during WWII.
It might not surprise you to learn that legend has it that the Castle is haunted. Author Gyula Krúdy, who lived at the turn of the 20th century and is renowned as a high authority when it comes to Budapest ghost tales, recounted the supernatural nightlife of the district. Once the roads clear as the residents head for the city, kings of the past supposedly emerge from the walls to wander the streets. Soldiers walled into the buildings are heard laughing and drinking, while ladies with golden shoes are looking for their knights in shining armor.
Beyond such fanciful tales, the castle over the course of its history has been the scene of violent murders. The central square even served as the site for executions in medieval times. It was also the site of what we might call the first modern murder to cause national outrage in Budapest in 1883.