The article explores how rainwater harvesting has evolved into rainwater management systems. It reviews past technologies and shows how rainwater can be a valuable water source. The term "rainwater harvesting" no longer fully describes the range of technologies used. The study presents a model where rainwater management systems are used to control stormwater. Examples worldwide show the success of smart rainwater management systems. A case study in Palermo, Sicily, demonstrates the benefits of different rainwater management types. Overall, rainwater management systems can help cities cope with water shortages, extreme weather, and climate change.