This paper provides a survey of ancient and traditional rainwater harvesting applications as effective climate adaptation strategies. Rainwater harvesting has a more significant past than a present. The fifteen identified ancient and traditional rainwater harvesting practices and the societies that practiced them may provide a key water conservation strategy for the future in vulnerable regions found in the dry-wet, semi-arid, and arid climatic regions. In the past several decades, there has been a call from scientific and non-governmental organization communities to combine modern water systems and old rainwater harvesting methods or to modernize the existing rainwater harvesting knowledge to benefit human settlements facing water scarcity.