The round cave is the classic shape, a soft dome of felted merino wool with an open front a cat can duck into and vanish. The wool holds body heat, so it stays warm without a heater, and the firm felt keeps the dome from sagging when a cat leans on the rim.It comes in a wide run of colors and two sizes, so there is a fit for a kitten or a big lounger. Handmade, so no two are exactly alike.