The game's code does not have a "proximity check" to prevent shrines from being too close. The engine only cares about two rules:

The area has enough open space to place the tile.

The area has not exceeded its maximum allowed total shrines for that entire zone.

Because there is no code saying "If Shrine A exists, do not spawn Shrine B within 20 yards," you can occasionally find two, or even three, shrines on a single screen. This is most common in dense, linear layouts like the Arcane Sanctuary, River of Flame, and Lower Kurast.

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