Are you a member of a band of adventurers that would like to level up quickly and are willing to take risks? I know the perfect dungeon you can go to grind up some experience points.*
Live Science reports that scientists have discovered an enormous spider colony in a sulfuric cave on the border between Greece and Albania. The dense web covering the interior of the cave stretches across about 106 square meters, which is approximately the surface area of skin of 73 humans if the skin is removed from those bodies.
-via Daddy Warpig | Photo: Urak et al., Subterranean Biology
*The loot is probably poor, though--aside from what's left behind by previous adventurers.