High Force

The Tees falls twenty-one metres in a single drop here, which is among the largest unbroken falls in England, though several others are higher in total. The geology is the point: the river runs over the Whin Sill, a sheet of hard dolerite intruded around 295 million years ago, and where it ends the water drops onto softer limestone and sandstone below, all three layers visible in the cliff face around the plunge pool. The fall is retreating upstream as the softer rock erodes. In spate the whole width of the gorge fills and the river runs brown with peat; in drought it splits into two narrow threads. The Pennine Way runs along the north bank, from which the fall can be seen without paying. Low Force lies two kilometres downstream.

What you actually see

• The twenty-one-metre drop - a single fall among England's largest.
• The three rock layers - dolerite over limestone and sandstone in the gorge wall.
• The spate and drought extremes - a full-width torrent or two thin threads.
• The Pennine Way bank - a free view of the fall from the north side.

When to go

April to October for the walk; the fall is most impressive after heavy rain or snowmelt, typically late autumn to spring. Upper Teesdale's rare arctic-alpine flowers bloom in June.

Honest expectations

The main viewing path is on private land and charged, which surprises people, though the north bank is free with a longer walk. The path has steps and roots and is slippery. Water volume varies enormously and a dry summer gives a poor showing.

Nearby

Low Force and Bowlees are downstream; Cauldron Snout and Cow Green lie further up the dale.