Bottomless Pit: They aren’t quite bottomless1, but on Eliéra, there are three shafts which have been dug all the way through the flat (well, very flattened ellipsoid) not-a-planet. Falling down one would be… inadvisable.
1. Or, as Amy just pointed out to me, technically they are – finite, yes, just over 200 miles in depth, but they do have no bottom. They instead have two tops, and one midpoint where the gravity goes away and comes back in reverse.