Aflaj in old Birkat al Mawz.

"Aflaj" is the plural of "Falaj", which means "split into parts" in classical Arabic.
This irrigation system effectively divided the water among all the inhabitants; it flowed by gravity from their original sources to homes and cropland. The complex included watchtowers to protect it, but also mosques and other buildings.[2]

In 2006, five Aflaj Irrigation Systems of Oman were added to the UNESCO list of World Heritage Sites.