N. Kósa Judit - Szablyár Péter: Underground Buda - Our Budapest (Budapest, 2002)

Adam Clark's masterwork - the Tunnel under Castle Hill

Szent György tér, where a 39.5 metre deep shaft was sunk at the middle point of the future tunnel. The three arms met before the year was out, and the widening-out of the pits to their final diameter was begun. Indicative of the public's expectations and the builders' eagerness to hasten profits is the fact that as of 19 March 1854, it was allowed that "pedestrians cross the tunnel for the payment of a 2 pengő-krajcár admission fee on Sundays." On 6 March 1856, the Tunnel was permanently opened to pedestrians and a year later, on 30 April 1857, vehicles were allowed across, too. Until 1918, a fee was charged for "crossing". At the beginning, the Tunnel was sealed with enormous wooden gates for the night.

Noted social events of the late 19th century were the "tunnel balls", for the duration of which fun-loving citizens took possession of the establishment, which was getting increasingly busy during the day.

Already registered when the Tunnel was under construction, the great amount of water leaking in was to be a source of increasing troubles. A committee including eminent scientists and engineers tabled its proposals in a detailed report drawn up in 1908. According to the report, the tunnel had been bored in the Buda marl in such a way that it cut diagonally across the rock layers of varying thickness and impermeability, which had led to the seepage of significant amounts of water in a north-to-south direction.

Although plans for a drainage system had not been finished before 1914, when they were ready they were immediately followed by the commencement of construction work. Three drifts of a smaller section were driven parallel to the longitudinal axis of the tunnel: one, to the north, 15 metres above the vault-level of the lower drift. The two drifts running parallel to each other were connected with fifteen vertical shafts. The shafts were covered with close-meshed iron grill in the upper drift to provide for free air passage. Horizontal ducts lead from the lower drift into the Tunnel. Twenty to 100 metre long ducts of a smaller section start from the upper drift horizontally and at an angle of 20 degrees to dehydrate the rock mass surrounding the Tunnel. These are now covered with formed blocks made of concrete, but stratum water is allowed to leave via openings in the lower one-metre half of the walls and flow into the channel below the Tunnel through the conduits of the ducts. In places there are 20-30 centimetre straw stalactites hanging from the vaults, and there are calcsinter basins at the bottom of the ducts.

The Tunnel is not perfectly symmetrical: it is 349.66 metres long, its gateway at the Clark Ádám tér end is 10.73, while the other one at Alagút utca is

38