Buda Castle Tunnel
The Buda Castle Tunnel is where Chain Bridge is stored when it rains – this is a joke regularly told by Budapest tour guides. In terms of size this could actually be true, but the 350-metre long structure has a different function in reality. It has served as a link between Clark Ádám Square and Krisztinaváros since 1857, and it is a little known fact that a service apartment, the headquarters of the Chain Bridge bridge master, is also tucked away in the tunnel walls. The tunnel has two car lanes and a pedestrian lane as well, but you might want to pass up a walk in the exhaust fume filled air. Instead of venturing into the dark pit of Castle Hill, go down to the riverbank, make the trek up to the Castle, check out Marvelosa or climb up on top of the Tunnel itself.