It was founded by the Romans in AD 75 as Venta Silurum, a market town for the defeated Silures tribe. This is confirmed by inscriptions on the "Civitas Silurum" stone, now on display in the parish church. Large sections of the Roman town walls are still in place, rising up to 5 metres high in places. Historian John Newman has described the walls as "easily the most impressive town defence to survive from Roman Britain, and in its freedom from later rebuilding one of the most perfectly preserved in Northern Europe." In 1881, a portion of a highly intricate coloured floor mosaic or tessellated pavement, depicting different types of fish, was unearthed during excavations in the garden of a cottage.