What is the name of the angelic city visited in Diablo III's Act IV?

The High Heavens is the angelic realm visited in Act IV of Diablo III.

After the earlier acts take the player through locations in Sanctuary, Act IV moves into the celestial domain of the angels. The player fights through the besieged realm while confronting the forces of the Burning Hells and attempting to stop Diablo's assault.

The High Heavens are also called the Silver City in Diablo lore. They are the home of the angels and the seat of the Angiris Council, whose members include Tyrael, Imperius, Auriel, Itherael, and Malthael.

The Burning Hells are the opposing demonic realm, not the answer to this question. Westmarch belongs mainly to Reaper of Souls, while Sanctuary is the mortal world where humans live.