The river Lathkill rises just below Monyash and flows down to meet the Wye just below Haddon Hall. The valley it forms is one of the finest of the limestone dales and the upper part is a National Nature Reserve, in the care of English Nature. It is a famous trout-fishing river, and Izaak Walton declared it to be the 'purest and most transparent stream' he had seen.
In places the top part of the dale is quite narrow and part-filled with spoil from Ricklow Quarry, just on the north side. The quarry was worked for a stone called '
Below Lathkill House Cave the valley widens out into a grand, deep valley with steep, rocky sides. This becomes even grander when it is joined from the south by Cales Dale, where a footbridge spans the stream and there is the remains of an old sheepwash which was used until the 1940s. This area of the dale is rich in wild flowers, and in spring the sides of the dale can be covered with orchids and cowslips.
Below Cales Dale the sides of the Lathkill are partly wooded, an area known as Low Wood. The first of many weirs appears and there was once a mill near here. Low Wood merges into Meadow Wood and in places the river is dammed to form ponds for the fish. There are many water-based birds too - wagtails, dippers, waterhens and coots for instance.
After passing Over Haddon the river continues in a heavily wooded, steep-sided valley to emerge at Conksbury bridge, where the mediaeval bridge carries the Youlgreave road across the river. Here there are numerous fish-ponds and the character of the river softens, flowing in a gentler, less steep-sided valley to meet the Bradford at Alport and then continue another 3 kilometres to the Wye.