The mountains have been inhabited since Neolithic times and a number of typical monuments, in particular a series of passage tombs, survive to the present day. The monastery at Glendalough, founded in the late 6th century by Saint Kevin, was an important centre of the Early Church in Ireland. Following the Norman invasion in the 12th century, the Wicklow Mountains became a stronghold and hiding place for Irish clans opposed to English rule. The O'Byrne and O'Toole families carried out a campaign of harassment against the settlers for almost five centuries. Later the mountains harboured rebels during the 1798 Rising. Rebel activity died out after the construction of the Wicklow Military Road at the start of the 19th century and the mountains began to attract tourists to the ruins at Glendalough and to admire the mountain scenery.