The Hidden Cities is a historic term for the part-subterranean cities of the Kalkot Gorge, particularly Seqal, Sopeq and Sequb.
The cities were originally built in caves and hollows in the karst rock of the steep-sided river valley, so they were entirely hidden from sight to travellers journeying across the plains above. In modern times the gorge is much more cluttered and the cities far larger, mainly built on the plains above with only the docks areas being next to the river.