Every year , a million tourists make their way to this already much put-upon World Heritage site in Wiltshire , about 75 miles southwest of London . As long ago as the Bronze Age , graffiti artists hacked images of daggers and axes onto some of the stones . In the 17th century , the famous British architect Christopher Wren chiseled his surname onto a pillar in elegant lettering ; others weren 't so careful when leaving their marks .