Although the valley of Mallerstang lies outside the Yorkshire Dales National Park, geographically it belongs to the Dales, and is one of three valleys to begin at or close to Garsdale Head. The valley is surrounded by one of the largest areas of consistently high ground in the area, peaking at over 2,300 feet on High Seat to the east and Wild Boar Fell to the west. The valley contains the source of the River Eden, only a quarter of a mile to the north of the source of the River Ure at the head of Wensleydale. The valley is characterised by scattered farms, containing a single hamlet, at Outhgill, while the only village, Nateby, lies at the northern edge of the valley.
Despite its remote location and wild nature, Mallerstang contains two communication links, the B 6259 which runs from the Moorcock Inn at Garsdale Head along the valley to Kirkby Stephen, and the Settle to Carlisle railway, which reaches its highest point when it crosses Ais Gill, close to the source of the Eden.
Mallerstang contains two buildings rebuilt by Lady Anne Clifford – Pendragon Castle and Mallerstang Chapel at Outhgill. The square great tower at Pendragon was built during the twelfth century, and survived for two centuries before being burnt by the Scots in 1341, when it was already owned by the Clifford family.