The first permanent bridge between Pest and Buda was built between 1839 and 1849. William Tierney Clark of England was entrusted with the preparation and execution of the plans. The designer contractor contracted his namesake, 28-year-old Scottish engineer Adam Clark, to manage the site work as a construction engineer. Construction began in 1839.
The idea of a tunnel running through Buda Castle Hill came about at the same time the construction of the Budapest Chain Bridge began. The construction of the Buda Castle Tunnel, ie the Budapest Castle Hill Tunnel, began in 1853, and the ceremonial opening took place on April 30, 1857.
The tunnel, built with an egg-shaped vault, has a total length of 340 meters, a width of 9.5 meters and a height of 10 meters at the gates, and 8 meters in the middle.