Figs grow very well when placed on or grown over a rock. Root-over-rock designs are also very much admired by bonsai lovers.
Figs with their aggressive root systems easily tolerate being placed over a rock. The rock is covered with soil and the tree is allowed to grow vigorously to attach the roots to the rock. The soil is gradually removed over time to reveal the roots.
This Ficus microcarpa tree was collected with my bonsai friend David Fukumoto about 12 years ago and placed on the rock, roots initially covered by aluminum foil to protect the new roots. Over time the foil was removed and the roots were now air adapted.