Harrop Tarn lies to the west of Thirlmere reservoir, under the cliffs of Tarn Crags. It may have been a much larger corrie tarn originally but is now silting up heavily. The resultant marshland has been planted with conifer plantations.

It is easily accessible with a car park at Dobgill Bridge on the Thirlmere western shore road and clear (although steep) paths up to the tarn. Alternatively, a path runs from Watendlath via Blea Tarn.

My first visit was, unfortunately too late in the day, so Tarn Crags are heavily in shadow. Another visit is, therefore required - especially as I've since spotted Launchy Tarn, about a mile north-west, which was not on my original list.