Creswell Crags, England

Rock face with engraved lines. In the photo, the outlines of a deer and of horses’ heads are drawn with coloured lines to highlight the carvings that are difficult to see.

TRACING OF OVERLAPPED PETROGLYPHS, CRESWELL CRAGS, ENGLAND

Apparently, they are the oldest known rock artworks, since they date back to the ice age (43,000 years ago).