The foundations of the monastery were laid by Constantine the Great in 300 to 330 AD, but it was completely built in 1086 AD. In the monastery are kept the icons of Panagia ''Odigitria'' and ''Antiphonitria'', the icon of St. Stephen and about 110 manuscripts. Today it is inhabited by about 45 monks and celebrates St. Constantine and Helen on June 3 according to the Julian Calendar.