Secret doors have been a staple of dungeons since the beginning of the Age of Darkness, although by Ultima IV, they also became quite common in houses to shield off secret areas. This practice reached its peak in Ultima V, where it was necessary to search every wall in order to discover any secret doors that might be present, since the Peer spell was unable to reveal them. After that time, these doors became easier to spot, and were less common.
- Despite them being secret, in every game starting with Ultima IV, these doors are marked with an irregular pattern in the 2D-view. This does not hold true for the 3D-dungeons in Ultima I, Ultima IV and Ultima V.