Llandrindod Lake was originally a marsh, hemmed in between the hills of the Ordovician inlier and the surrounding Silurian rocks.
The Temple Street Erratic formed at the Elan Valley in the Silurian period, and was moved to Llandrindod by a glacier during the last ice age.
The Rhogo area exposes many important geological exposures, including unique fossil assemblages and a rich and well-exposed geological sequence through the beginnings of the most violent part of the creation of the volcanic island.
