Before Rome

In a flat basin near Walton in Radnorshire, sometime around 2700 BC, people dug a trench a mile and a half long and stood roughly fourteen hundred oak posts in it.

The Hindwell enclosure is among the largest structures of its kind known anywhere in Neolithic Europe. Nothing of it shows above ground. It was found from the air, as crop marks, and the Walton Basin as a whole has produced cursus monuments, henges, palisaded enclosures and a great deal else in a landscape that looks, from the road, entirely ordinary.

That is the useful lesson for prehistoric Powys generally: the visible monuments are the survivors, not the sample.

What is visible

Chambered tombs. Neolithic burial monuments cluster in the south and east, in the Usk valley and the Black Mountains, where the good land is. Gwernvale at Crickhowell sits in a hotel garden. Ty Illtud above Llanhamlach carries medieval graffiti cut into its stones by people who found it already ancient.

Standing stones and cairns. Bronze Age, and everywhere, mostly on the ridges. The pattern is consistent across mid Wales: burial and ceremonial monuments on the high ground, settlement on the lower ground where it has since been ploughed away. The uplands look empty of prehistory only if you assume the monuments were where people lived.

Hillforts. The Iron Age is the period Powys has in abundance. Ffridd Faldwyn above Montgomery, Pen y Crug above Brecon, Crug Hywel above Crickhowell, Caer Din, the Breiddin. Some are enormous multi-rampart affairs; many are small enclosed farmsteads that the term "hillfort" rather oversells.

What that adds up to

The county was well populated and organised long before anyone wrote about it. The Breiddin, on the Severn near Welshpool, was occupied from the late Bronze Age and produced metalworking evidence, imported goods and a long sequence of rebuilding.

Two things are worth holding on to. The first is that the tribal territory the Romans encountered here — the Ordovices in the north and west, the Silures to the south — was not a blank space they moved into. The second is that a great deal of what survives above ground does so because it is on land too poor or too high to have been ploughed since, which biases everything.

Where to see it

The Walton Basin has an interpretation panel and very little else, which is oddly appropriate. Pen y Crug is an hour's walk from Brecon and gives the clearest hillfort earthworks in the county for the effort involved. Crug Hywel above Crickhowell is the most photogenic.

For chambered tombs, the Black Mountains group repays a day. For upland cairns, any of the ridge paths in Fforest Fawr or on the Berwyn will put you past several without signage of any kind.