Monasteries were a place of seclusion and prayer, developed by many sects and churches in human history, notably Hinduism, Buddhism, and Christianity. Greatly varying in size and appearance, they were usually inhabited by individuals of one specific gender, who typically practised celibate and poverty. Some monastic organisations also had other functions, like tending to the poor, teaching, or evangelism. The oldest known Monasteries were Buddhist vassas originating around 4th century BC, which were originally temporary but with time became quite permanent. Some Monasteries grew unusually big: the Cappadocian Caves in Greece are known to have accomodated over 5,000 monks, while the Drepung Monastery in Tibet housed around 15,000 monks before the Chinese invasion.