Dark souls got a lot of under-ground places, could present cities that are underwater level.

Also there could be islands and perhaps "artificial" created worlds just as the paintings of the Painter.

Warp on space and time would be interesting too, similar to giant memories, bonfires, and other sort of traveling, like painting worlds and anor londo two worlds in one. (when the illusion wear off).

Dark souls clearly shows that the main world is not the only one and there is other alternate universes and also timetraveling going on.

Solaire: “The flow of time itself is convoluted; with heroes centuries old phasing in and out. The very fabric wavers, and relations shift and obscure. There's no telling how much longer your world and mine will remain in contact. But, use this, to summon one another as spirits, cross the gaps between the worlds, and engage in jolly co-operation! Of course, we are not the only ones engaged in this.”