can you expand a little on that....is there any soil ? is it shallow, dry, full sun ????

I suggest Buddleja, it seems to grow out of anywhere.

Cistus, sometimes called Rock Rose although other plants also are, is a shrub that naturaly grows in stony place around the Mediteranean.

Lavender and rosemary might be worth a try too. And sedums & sempervivums.

Helianthemums too!