[Elmo]

Just in case you don't know the subdivide function is awesome and is how I made the warpath map. Every edge should match up one to one else you'll get gaps. Matching edges two-to-one (two 128 brushes on a 256 brush) does work but you need to remember to sew it after using subdivide.

First thing first to see what it does is to make a block as a cube, do 64 or 128 square. Select it all and make it all displacement and with it all selected click the subdivide button. You now have a sphere! Whoop.

Next thing is make... the corner of a room (floor and two sides) match every edge one to one. So use 3 128x128x32 brushes for example. click the 3 faces and you'll get an inward curve.

I'm sure there are tutorials on subdividing somewhere but I never came across any. They're really good to shape the area and then you go along with the usual manipulation tool after.