Dark Gate

The Dark Gate (or alternatively Dark Portal, Hungarian: Sötétkapu) is a tunnel located under the artificial slopes of Castle Hill near St. Adalbert's Basilica in Esztergom, Hungary. The tunnel is 90 metres long and follows the line of the castle's former eastern walls. The entire tunnel is vaulted and built in Neo-classical style.

Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).