[1] The escarpment is the remnant of quarrying that had begun by the mid-18th century and initially provided limestone for building and agriculture as a fertiliser, and subsequently for the blast furnaces of the local ironworks as a flux.

Ogof y Daren Cilau is one of the longest cave systems in the United Kingdom (over 26 kilometres/16 miles in total) and the entrance section is long, tight and strenuous, making the trip into the further parts of the cave a serious undertaking.

[3] Its awkward 517-metre (1,696 ft) entrance crawl is a natural barrier to any casual visitor and precludes the need for a locked gate to protect it from vandals.

In the ensuing period, the water was drained away and a 400-foot (120 m) passage was revealed ending in a boulder choke.

[4] In 1986 Martyn Farr connected the Terminal Sump to Elm Hole in the next valley by cave diving.