This is one of the geological and scenic highlights of the Peak District National Park. Alport Castles is said to be the largest landslip in Britain, but it is rarely visited because of its remoteness.
The Alport Valley is made up of weak Carboniferous shales (fine-grained rocks made of mud) overlain by harder Millstone Grit. The large cliff face we see here is the Birchin Hat escarpment. Alport Castles formed when the softer sandstones and shales of Birchin Hat slipped away from the rock-face. The Millstone Grit on the top broke up into blocks and tumbled down the valley side, creating a chaotic landscape of fallen boulders. With a little imagination, they can resemble castles – hence the name.
The most impressive feature is named The Tower, an isolated rock pinnacle which looks for all the world like a man-made medieval fortress. Beneath The Tower lies one of the Peak’s only true mountain tarns, known as Alport Mere.
But what caused the landslide? It’s thought that water seeping between the cracks in the gritstone and shale weakened the shale and caused it to slip away. The gritstone is naturally full of joints so it breaks into blocks when the shale below becomes unstable.
Frost and ice during the Ice Age would have accelerated this process. Glacial erosion could have also over-steepened the side of the valley, causing it to slip away as the glacier melted.
In recent years Alport Castles have become the regular nesting site for peregrine falcons. These dashing raptors, revel in the peace and solitude here, so you might be lucky enough to spot one soaring beneath the crags.
Next, follow the faint footpath which leads down to a crossing of the Alport River near Alport Castles Farm.
This trail was originally created by Roly Smith for the Royal Geographical Society’s Discovering Britain. Thanks are also due to Helen Rawling for editing the walk and to Chris Speight FRGS, CGeog, RGS-IBG Trustee for checking the route and providing feedback.
Roly is a keen walker and the author of over 90 books on the British countryside. He has been recently described as one of Britain’s most knowledgeable countryside writers.