In the eastern area of the 543-meter elevation of the Jaizkibel massif, near Gaintxurizketa-Guadalupe, J. M. de Barandiarán discovered, in 1934-1935, two dolmens which were later destroyed by road construction. Findings made over the past twenty years in the maritime perimeter of Cape Higuer seem to confirm the suspicions of Berrotarán and Díaz in 1785 (report to the Academy of History), recorded by Serapio Múgica, regarding the existence of port-type settlements in the Bidasoa estuary, which is now rapidly silting up, but which in Roman times appears to have formed an estuary reaching Endarlaza, an active site for navigation and coastal trade.
Archaeological and toponymic remains are not limited to the transverse courses of Jaizubía, Ibarla, and Estebenea. Mezquiriz, Hernandorena, and Rodríguez Salis have found, in the anchorage of Asturiaga (towards Higuer), a series of Roman archaeological materials, especially ceramics, in front of the castle of San Telmo. These findings, together with important discoveries in Irún by J. Rodríguez Salís, have led scholars like I. Barandiarán to suspect “that the site of Juncal and what may be discovered nearby corresponds precisely to the urban core of that Oiason of the Vascones which, due to the Era change, was connected with the Romans” (Guipúzcoa in Ancient Times, CAP, 1973, p. 84).
Oiason thus appears as a polyvalent designation. According to Barandiarán, it would correspond to a city, a cape or promontory, and a passage Iberia and Aquitaine. Adolf Schulten, guided by his interpretation of a passage from Avienus’ Ora Maritima, conducted an excavation in 1926 under the old hermitage of San Telmo in search of a maritime temple to Venus (Veneris iugum). The famous German archaeologist found an ancient structure that led him to reaffirm his thesis, even though it was challenged by various authors who, based on the mention of two rocks – Amuitz and Les Briquets for Schulten – considered them insignificant to be those referred to by the classical chronicler.