The approximately 40 hectares surface area of the Castle Hill, that is surrounded by thick man made walls, rises as a mesa between the valleys carved by the Danube River and the Ördögárok (Devil's Ditch) Creek. The main mass of the hill is made of so called Buda Marl. This rock material that resembles clay is of good stability but this stability drops to one fourth, one third of the original value when it gets wet.
The Ördögárok Creek used to trickle at the elevation of the present hilltop in the geological age of the Quaternary and deposited a pebbly sediment on the top of the marl that vas covered later by a 7-12 meter thick layer of freshwater limestone by rising thermal springs. This hard layer of rock prevented later the weathering of the Castle Hill. The freshwater limestone is thickest at the Szentháromság
People used to live on the top of the Castle Hill even before the raising of the Buda Castle. The inhabitantss of the medieval hamlet probably happened to find the caves hidden in the depth while digging wells. Utilizing the natural potentiality they cut access tunnels to the cavities and turned them to cellars. The investigation of the cavewells revealed finds hinting the 11th or 12th centuries. It's been suggested that the very arrangement of the houses on the surface was adjusted to these cave cellars.
King Béla IV ordered the raising of the Buda Castle, the new residence of the sovereign in the spring of 1242, after the Mongol invasion. The builders of the early Medieval had two purposes in mind: defend the residents from the enemy and provide the basic needs within the walls. While the external defense was provided by bastions 5 to 10 meters high the provision of water was most practical from the resources in the caves. The wells in the cave-cellars provided potable water in the times of sieges. The caverns under the houses were well-suited for other purposes like the storage or rather hiding of food reserves and valuable from the enemy -or from the tax collector. Many of the cave cellars were used as ice-pits in the times of the Turkish occupation.
The caves had important roles in the times of calamities: major fires, wars, sieges. According to some opinions the defending troops could be moved under the ground. A number of recitals depict troops attacking the enemy through tunnels dug ti the feet of the bastions from cave-cellars.
Evlia Chelebi, Turkish traveler characterizes adequately the Buda castle as "being hollow". Rumors got around that some Turkish high officers made odalisques that they got tired of "vanish" in the depths. Many roamed the cavities to find buried Turkish treasure. Research people of our days did not find remains of odalisques or treasures, but only rusty spurs, broken pottery or ancient cannon balls on occassion. Most cave-cellars had been forgotten in the 19th century. Imagination placed the dens of "Black Barons", or spirits under the ground. Moreover the neglected cavities caused more and more trouble. Because of collapses of street pavement the mapping of the cave-cellar system was ordered in the late 1800-s. The final verdict was to fill the cavities with debris, trash or soil.
Dr. Ottokar Kadic, the eniment speleologist of the era recognized in the 1930-s that the cavities called "Turkish Cellars" were natural freshwater-limestone caves. He prepared a project to clean the cave-cellars and turn them presentable to the public. Also he persuaded the leadership of the 1st City District of Budapest to back the idea.
With man made wall brakes and "adits" an increasing number of cavities were joined. It happened during the making of such a tunnel that Dr. Kadic discovered the primitive chert tools that ascertain that ancient man settled in the vicinity of the hot springs.
After the beginning of World War II bomb shelters were developed from the cellars, tourism was terminated. By the making of new corridors, and reinforcing the existing cellars a bomb shelter labyrinth of kilometers in length was developed. The hitherto operable "Rock Hospital" was developed in that historical period. According to records more than 4000 people found refuge in the Castle-cellars in the hard days of World War II.
The Castle Cave reached its maximal development beyond four kilometers in the nineteen fifties. Much of the labyrinth was classified top secret. The system doesn`t suit modern civil defense requirements any more. Speleologists, cavers achieved at the beginning of the 1960-s that part of the system be reopened for the public, but for the lack of founds it was closed up again in 1975. Since then the cave-cellars system that is rich in natural and historic values was declared to be one of the Hungary`s "exceedingly protected" caves.
Street pavement subsidence and such effects turned the attention again to the problems caused by the cave-cellar system. The system was inspected, reinforced at locations of need and surface automobile traffic was restricted.
Presently most of the troubles are caused by independent cave-cellars. The location and condition of most of these cellars is unknown. As they are filled in, their inspection and examination demand much energy and funds. Some can be located only following up the stories of residents or studying old maps, some are filled by wartime debris.
The atmosphere of the medieval cave-cellars have been preserved in spite of man made intervention. Their original appearance can be studied in the more than fifty independent cellars at the northern part of the Castle District. The cellar system of the Castle is of three kinds. Under the cellars belonging to the houses arched medieval deep cellars are located carved into freshwater limestone. Entries to the lowermost natural cavities open from this second level. These letter were only deepened by the old time residents but some reinforcement: pillars, arches can also be met. The whole sequence of the Castle Hill geology can be observed on the cellar-wals: layers of marl, the pebbly-clayey deposit of the ancient Ördögárok Stream are exposed at varying locations. The deep wells expose the hydrological conditions of the hill.
