O'Rahilly claims that it was probably as a result of the Laginian conquests that Ireland first came to be divided into four provinces. The Érainn continued to rule in Ulster and Munster, while the Lagin and their allies became the dominant force in Leinster and Connacht. Traditionally these four provinces met at the exact centre of the country, which was marked by the Hill of Uisneach (between Mullingar and Athlone in County Westmeath), a name which may mean "vertex" or "angular place". The district immediately surrounding this hill was originally called "Medion" "middle", and is the origin of the name of County Meath. Julius Caesar informs us that the druids of Gaul regularly assembled at a hallowed spot in the centre of Gaul to celebrate their rituals ("De Bello Gallico" 6.13). Irish tradition records that a similar assembly, the Mórdáil Uisnig, periodically took place at the Hill of Uisneach on Beltane, the May-day festival.