Gilwern Hill is a hill about 3 mi / 5 km southeast of Llandrindod Wells

Llandrindod Wells

Llandrindod Wells , colloquially known locally as "Llandod", is a town and community in Powys, within the historic boundaries of Radnorshire, mid Wales, United Kingdom. It was developed as a spa town in the 19th century, with a boom in the late 20th century as a centre of local government. Before...

 in the county of Powys

Powys

Powys is a local-government county and preserved county in Wales.-Geography:Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire , and a small part of Denbighshire — an area of 5,179 km², making it the largest county in Wales by land area.It is...

, Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

.

Geology

The hill is composed from a range of lower and middle Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 volcaniclastic rocks which form a part of the Builth Inlier. Palaeontologists Pete Lawrance and Brian Beveridge have spent 30 years examining fossils from a privately-owned limestone quarry on the hill. Amongst fossils so far identified at this location are the trilobite

Trilobite

Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...

s Meadowtownella

Meadowtownella

Meadowtownella is a rare species of Trilobite found in Ordovician rocks. It is similar to Acidaspis cincinnatiensis but without the occipital spine....

, Bettonolithus

Bettonolithus

Bettonolithus is a Trilobite of the Order Asaphida. It is in the family Trinucleidae.Fossil specimens have been found in the Lower Ordovician rocks of Gilwern Hill in Powys, Wales....

, Protolloydolithus

Protolloydolithus

Protolloydolithus is a blind Trinucleid trilobite found in Ordovician rocks in Gilwern Hill, Powys, Wales.-Features of Trinucleid Trilobites:-References:* The World Encyclopedia of Fossils& Fossil-Collecting, Steve Parker*...

 and Anebolithus

Anebolithus

Anebolithus is a Trinucleus species of Trilobite found in Gilwern Hill, Powys, Wales.-Features of Trinucleid Trilobites:-External references:http://www.kgg.org.uk/anebolithush.html...

 together with Conulariida

Conulariida

The Conulata, also known as conulariids, form a poorly understood clade of extinct scyphozoan cnidarians.-Structure:The conulariids are fossils preserved as shell-like structures made up of rows of calcium phosphate rods, resembling an ice-cream cone with fourfold symmetry, usually four...

, Iocrinus

Iocrinus

Iocrinus is an extinct genus of crinoid .This genus is an early form of crinoid, from the Ordovician rock of Gilwern Hill, Powys in Wales....

, Clonograptus

Clonograptus

Clonograptus is a genus of Graptolites. Groups of these animals were connected by stalklike structures to a central region. Species of Clonograptus are zone fossils, that help us estimate a precise age of Ordovician rocks....

 and starfish 

Stone rows

There are two prehistoric stone row

Stone row

A stone row , is a linear arrangement of upright, parallel megalithic standing stones set at intervals along a common axis or series of axes, usually dating from the later Neolithic or Bronze Age. Rows may be individual or grouped, and three or more stones aligned can constitute a stone row...

s at the southern end of the hill, each with a large stone, more than 2m high, at one end.