In chronostratigraphy, the British sub-stage of the Carboniferous period, the 'Arundian' derives its name from Hobbyhorse Bay in the Castlemartin community—arundo being the Latin for hobby horse.

[3] Castlemartin has 8 miles (13 km) of coastline, much of it consisting of spectacular limestone cliffs characterised by large sea caves, natural arches and stacks.

The village of Castlemartin was in the ancient Hundred of the same name, once centred on a prominent Norman motte-and-bailey castle giving, with the church dedicated to St Martin, the origin of the name.

Here, the Pembrokeshire Coast Path has to run inland; by-passing many interesting sections of cliff, although sometimes access may be offered to Flimston.

In 2011, the MoD opened up a special diversionary route which was safer for walkers by protecting them from the range fire and preventing them for having to negotiate narrow country roads with fast moving traffic.