I've always loved visiting hot springs. There's something so relaxing and striking about the difference in scenery from spring to spring; and the coolest part is that many have health benefits! While I might never get the chance to witness Badab-e Surt in Iran first-hand, it's going to remain on my bucket list.
The natural site in the Mazandaran Province (the northern part of the country) is comprised of stepped travertine (a type of sedimentary rock) terraces that have formed over thousands of years. As flowing water from two mineral hot springs cooled and deposited carbonate minerals on the mountainside, Badab-e Surt grew.
The springs sit over 6,000 feet above sea level. Each carries interesting, yet quite different, properties: The first spring consists of extremely salty water that is considered to have medicinal properties (supposedly it cures rheumatism and various skin conditions). The second spring is apparently sour to the taste and is orange due to the large iron oxide sediments in it. If the travel advisory for Iran is lifted in the future, this is one of the first spots I'll check out in the country!