The Whin Sill is one of the North's most distinctive features.
This rocky outcrop is part of a huge sheet of rock which starts at the Farne Islands and runs along the Roman Wall and then under the Pennines.
Molten rock was pushed up from the earth's surface, cooled, crystallised and formed the Whin Sill as we see it today.
One of the best places to see the Whin Sill is close to Housesteads Fort, one of the best preserved Roman sites in Britain.
Housesteads lies on the great volcanic escarpment of Whin Sill. It is one of the 12 forts added to the Wall in about AD124, and was designed to contain a garrison of 800 soldiers.
There are stunning views from the Whin Sill on a clear day to Scotland, the north Pennines and the North East of England.