by the apparition of longhouses of ultimately north European tradition which were replaced later in much of Galicia by roundhouses. By the 4th century BCE hill-forts have expanded all along Galicia, also on lowlands, soon becoming the only type of settlements. These hill-forts were delimited usually by one or more walls; the defences also include ditches, ramparts and towers, and could define several habitable spaces. The gates were also heavily fortified. Inside, houses were originally built with perishable materials, with or without a stone footing; later on they were entirely made with stone walls, having up to two storeys. Specially in the south, houses or public spaces were adorned with carved stones and warrior sculptures. Stone heads, mimicking severed heads, are found at several locations and were perhaps placed near the gates of the forts. A number of public installations are known, for example saunas of probable ritual use. Of ritual use and great value were also items such as bronze cauldrons, richly figured sacrificial hatchets and gold torcs, of which more than a hundred exemplars are known. This culture is now known as Castro Culture; another characteristic of this culture is the absence of known burials: just exceptionally urns with ashes have been found buried at foundational sites, acting probably as protectors. Occasional contacts with Mediterranean navigators, since the last half of the second millennium BCE, became common after the 6th century BCE and the voyage of Himilco. Punic importations from southern Spain became frequent along the coast of southern Galicia, although they didn't penetrate very far to the north or to the interior; also, new decorative motives, as the six-petal rosettes, are popularized, together with new metallurgical techniques and pieces (ear pendants) and some other innovations as the round hand mill. In exchange, Punics obtained tin, abundant in the islands and peninsulas of western Galicia (probable origin of the Cassiterides island myth) and probably also gold. Incidentally, Avienus' Ora Maritima says after Himilco that the Oestrymni (inhabitants of western Iberia) used hide boats to navigate, an assertion confirmed by Pliny the Elder for the Galicians. Roman conquest First recorded contact with Rome happened during the Second Punic War, when Gallaecians and Astures, together with Lusitanians, Cantabrians and Celtiberians —that is, the mayor Indo-European nations of Iberia— figured among the mercenary armies hired by Hannibal to go with him into Italy. According to Silus Italicus's Punica III: Fibrarum, et