The Antonine Wall, the northernmost boundary of the Roman Empire, is located in Scotland. The wall was built by the Roman Empire in the 2nd century AD as a defense against the northern tribes in Britain. It stretched for about 37 miles (60 km) from the Firth of Forth to the Firth of Clyde and was the northernmost limit of Roman expansion in Britain. The Antonine Wall is now a UNESCO World Heritage Site and is considered one of the most important Roman archaeological sites in Britain.