The best is in the Sahara desert, particularly in Niger's Air mountains, in the Tibesti mountains of northern Chad and southern Libya, and in south-east Algeria's Tassili n'Ajjer range.
TARA's founders, raves about a recent find in the Tassili n'Ajjer range: an anatomically perfect four-metre-long carving of a hippo hunted by an Egyptian-looking figure with a superbly sinuous bow.