Finally, the sun came out (and then in and then out and then in again, as it is prone to do on an English summer day!) I headed to Malham Tarn, a large glacial lake above the famous Malham Cove. At 375 metres above sea level it is England's highest lake and is a rare example of an alkaline lake, sited as it is in an area of limestone. Geologically interesting and supporting many rare flora and fauna, the area is owned and managed by the National Trust, and Tarn House is used as a field studies centre. The lake is drained by a small stream that disappears underground into a huge network of caves and tunnels through the limestone and reappears beyond Malham Cove to form the source of the River Aire... here today, flowing through Saltaire sometime thereafter.
You can take a lovely circular walk round the tarn, passing through a variety of areas of interest.