St Columb's Cathedral was built between 1628 and 1633 and is the oldest surviving building inside the city walls. It is the cathedral church of the Church of Ireland diocese of Derry and Raphoe, and it has been a central landmark in the city's Protestant identity since the plantation era.
The building is relatively plain on the outside — a Gothic revival tower added in the nineteenth century somewhat breaks the original impression — but the interior is more interesting, with fine Victorian stained glass and the chapter house displaying artefacts from the 1689 siege including the famous cannonball. The cathedral also has good views from its grounds back toward the walls and the Guildhall. Entry is by donation.