Ledges

When building in my vault I discovered that the vault doorway is not infinitely high. It even has a ledge above it. Since a player can't reach these from the vault floor, it allows items to seemingly float in air.

I tested the door to Tavelor's bar. It does have a finite height, but no ledge.

The orc cave entrance has a ledge:

This ledge has an extra feature, the ability to fall into the void. Ways of doing this have been found in the past, but they've been patched, which is probably a good thing since it allows "wanted" players to log out without waiting.

I left a single floating boot up there.

My vault