These beau­ti­ful traver­tine ter­races in north­ern Iran are an incred­i­ble nat­ur­al phe­nom­e­non that devel­oped over thou­sands of years. Traver­tine is a type of lime­stone formed from the cal­ci­um deposit in flow­ing water, and in this case it’s two hot springs with dif­fer­ent min­er­al prop­er­ties. The unusu­al red­dish colour of the ter­races is caused by the high con­tent of iron oxide in one of the springs.