One of Turkey’s most famous natural wonders, the pure white travertine terraces of Pamukkale (“Cotton Castle” in English) cascade down the slope looking like an out-of-place snowfield amid the green landscape. Although the travertines are themselves a highlight of a Turkey trip, the vast and rambling ruins of Roman Hierapolis, an ancient spa town, lie on the top of this calcite hill, providing another reason to visit. For the best photographs, come at dusk when the travertines glow as the sun sinks below the horizon.