A worked-out chalk quarry near Pitstone, flooded and left to nature, College Lake is now a reserve of open water, reedbed and chalk grassland run by the local wildlife trust. Hides look over wetland birds, and there’s a visitor centre and café by the shore. Entry is free. Tring station lies about 3km to the south-east.

© Rob Farrow / Geograph · CC BY-SA 2.0