Christianity introduced simple monastic houses, such as Clonmacnoise, Skellig Michael and Scattery Island. A stylistic similarity has been remarked between these double monasteries and those of the Copts of Egypt. Gaelic kings and aristocrats occupied ringforts or ''crannógs''. Church reforms during the 12th century via the Cistercians stimulated continental influence, with the Romanesque styled Mellifont, Boyle and Tintern abbeys. Gaelic settlement had been limited to the Monastic proto-towns, such as Kells, where the current street pattern preserves the original circular settlement outline to some extent. Significant urban settlements only developed following the period of Viking invasions. The major Hiberno-Norse Longphorts were located on the coast, but with minor inland fluvial settlements, such as the eponymous Longford.