Maeshowe is a large Stone-age burial chamber in the Orkney Iskands (off the north coast of Scotland) from 5000 years ago. When antiquarians broke into the chamber in the 19th century they found they weren't the first such visitors. The walls were covered in runic graffiti from the 12th-century -- the islands having long been under Viking/Norse control. You can read some of them here. Some highlights are:

• "Tholfir Kolbeinsson carved these runes high up"
• "These runes were carved by the man most skilled in runes in the western ocean"
• "Ingigerth is the most beautiful of all women" (carved beside a rough drawing of a slavering dog)
• "Thorni f*cked. Helgi carved"