The first examples of urbanization in Celtic Europe were the princely residences of the early Iron Age, but it was not until the late third century BC that urban centres began to flourish across Europe. The first were open settlements, followed by fortified oppida. Characterized by very large surface areas (up to hundreds of hectares) and defended by ramparts with strong symbolic and ostentatious connotations, oppida are widely considered the first cities north of the Alps. Craft and commercial activities were prominent, but they were also important political and religious centres, displaying a coherent internal organization, with functional zoning and public spaces. Oppida appeared in the late second century BC, disappearing in the mid-first century BC in the east, but surviving until the Augustan period in Gaul. The structuring of Gaulish civitas territories implies that some oppida were true capitals.