A short walk from Forua railway station, on the western shore of the Urdaibai estuary, lie the foundations of a Roman port settlement that flourished from the first to fourth centuries AD — one of the only Roman sites visible in coastal Biscay. The excavations have uncovered iron-smelting furnaces, a market hall, and a forum with paved streets.
A small interpretation centre on site explains the trade in iron and salt that supported the town. Free entry; combine with a visit to the bird centre upstream.