Sheffield is a geographically diverse city. Lying in the eastern foothills of the Pennines, the city nestles in a natural amphitheatre created by several hills and the confluence of five rivers: Don, Sheaf, Rivelin, Loxley and Porter. As such, much of the city is built on hillsides with views into the city centre or out to the countryside. Blake Street, in the S6 postcode area, is the third steepest residential street in England, with a gradient of 16.6°. The city's lowest point is just above sea level near Blackburn Meadows, while some parts of the city are at over ; the highest point being at High Stones, near Margery Hill. However, 79% of the housing in the city is between above sea level.