At Knossos on the island of Crete in Greece there's a superb Minoan palace which was discovered by Sir Arthur Evans in the late 19th Century. It dates from neolithic times.
When I visited it (in the sixties) there were the most wonderful frescoes of dolphins, athletes jumping over bulls and topless ladies with elaborate plaited hair-dos. Even the fat pillars were painted a rich red.
Only afterwards did I learn that all this had been 'restored' from faint, fragile shadows of their art. :(