Temple of Singularity

The Shrine of Singularity was a gargoyle shrine, dedicated to their most important Virtue, Singularity. Located in the Realm of the Gargoyles, it was the most holy place of the gargoyles, and could only be reached by means of flight over a range of mountains. The shrine once housed their three sacred books: the Codex of Ultimate Wisdom, the Book of Circles and the Book of Prophecies.

History
Though it wasn't mentioned in Ultima IV, this is the place the Stranger reached at the end of that game after getting to the bottom of the Abyss, as this is where the Codex rested at the time of the Quest of the Avatar. This place was revealed to be the Shrine of Singularity in Ultima VI. The Codex of Ultimate Wisdom was taken by the Great Council from the Shrine of Singularity after the events of Ultima IV, and moved into the Shrine of the Codex.

During Ultima VI, the Avatar reached the Shrine of Singularity by means of a Hot-Air Balloon. Once the Avatar proved knowledge of who deserves to keep the Codex, and learned of the Gargish Principles of Control, Passion and Diligence, the Shrine of Singularity granted this quest:

''"Let the principle of control guide thy quest. Let the principle of passion drive thy quest. Let the principle of diligence maintain thy quest. Then wilt thou truly achieve the unified spirit and singularity of purpose that is necessary for success in all endeavors. This is the gargoyle way; let it be thy way as well." The altar glows with a cold blue flame. You feel compelled to seek out the Codex.''

As with the rest of the Realm of the Gargoyles, the shrine was probably destroyed after the events of Ultima VI.

Trivia

 * The Shrine of Singularity is the only shrine in Ultima VI that can get you into the presence of the Codex.