From the Bronze Age there are extensive examples of rock art. These include cup and ring marks, a central depression carved into stone, surrounded by rings, sometimes not completed. These are common elsewhere in Atlantic Europe and have been found on natural rocks and isolated stones across Scotland. The most elaborate sets of markings are in western Scotland, particularly in the Kilmartin district. The representations of an axe and a boat at the Ri Cruin Cairn in Kilmartin, and a boat pecked into Wemyss Cave, are believed to be the oldest known representations of real objects that survive in Scotland. Carved spirals have also been found on the cover stones of burial cists in Lanarkshire and Kincardine.