Badab-e Surt looks like Pamukkale dipped in rust — the same kind of stepped travertine pools built by mineral water, but glowing orange, brick red and ochre instead of Turkey's snow-white. Two springs feed it, rising separately from the slope near Orost village in northern Iran: one heavily salted, the other sharply sour and loaded with iron, which stains the rock its fiery colour. Where the two waters spread and cool, they have built hundreds of shallow basins that descend the mountainside like a natural staircase, one spilling into the next. The name says it plainly: badab means 'gassed water' in Persian, for the fizzing carbonated springs, and Surt is the old name of the village. Geologists trace the terraces to the Pleistocene and Pliocene, and in 2008 Iran registered the site as its second national natural monument, after Mount Damavand.
Sit at the edge of a pool and look down the slope: each step holds a sheet of still water that mirrors the sky and the wooded hills behind, and the whole staircase changes colour as the sun moves — copper at one hour, gold and crimson at another. Light is everything here. At dawn and sunset it rakes low across the terraces and picks out the fine mineral lacework frozen along every rim. Set at 1,840 metres in the Mazandaran mountains, about 95 kilometres from the city of Sari, the place stays cool, quiet and far less crowded than Iran's headline sights — and it carries no UNESCO protection, which leaves its fragile crust more exposed than most. For now it remains one of Iran's quietest wonders, a sculpture of coloured stone that water is still slowly building.