Impossible Architecture in Minecraft (multiplayer compatible)

I did this once using Mystcraft, recreating the Ahnonay Cathedral (from Uru). I don't have any video of it in action, unfortunately.

Original thread on the Mystcraft forums.

Screenshots:

• The cathedral itself:

• The three "time" ages:

  

The way it was constructed was such that where you spawned in (where the player is standing, first pic) is the nexus of a proximity detector (at the time built using spawners, there are much better ways now, including command blocks).

When the player left the zone (went towards the linking book at the end of the long hallway) the proximity detector would trigger and pistons would close off the passage and reopen another copy 90 degrees rotated. The player would never hear it happen because of how far away they were. And as the only way out was forward, they had no reason to turn around, either (the central chamber having no other apparent exits).

I could have cheated and used 3 different overworld locations as well as 3 different dimensions, but this worked such that no matter how the player returned to the Cathedral itself it would ALWAYS rotate once.

In theory you could pull off something similar with Nether and End portals. Hmm, that might actually work pretty well: use the End as the cathedral hub (the location that is always the same) and then have the "arms" be at the overworld spawn area (closed off using the proximity detector) leading to different nether portals, placed far enough apart to link to different areas of the nether. It'd be particularly convincing as the End portal will always link back to the same location and you'd have up four possible alternatives.