Altar rooms

The altar rooms are found in Ultima IV on the eight level of the dungeons of Britannia.

There are three of them, each dedicated respectively to the three principles of Truth, Love and Courage. Each altar room has four entrances, from the four dungeons representing the anti-forces of the virtues that the principle creates. For example, since Honor comes from Truth and Courage, the dungeon Shame has access to these two altar rooms. The dungeon Hythloth, opposing Spirituality, has access to all three of them.

In Ultima IV the Stranger had to enter the three altar rooms and use the fitting Virtue Stones on them in order to get all pieces of the Key of Three Parts. After that time, the altar rooms weren't seen again.

Pratical Considerations
The easiest way to access all three altar rooms is, to enter Hythloth through the ladder in Castle Britannia, which directly leads to level 8, where all three rooms are available. After getting the key, go through the altar rooms to a dungeon with an easy to reach entrance (like Despise) and then cast Xit to leave.

The connections between the various dungeons and the altar rooms are shown on the diagram on the left.