Ground Cover Creeping Sedum - fast-spreading, drought tolerant and easy to keep in check. It grows in the hot, full sun or in the shade. It doesn't seem to have any special soil requirements. In June, it's covered with tiny yellow flowers.
I love all of this - outdoor fire pits and the modern idea of combining stepping stones as a staircase along with the gray that is really popular in design everywhere right now makes this landscaping look great!