On the surface they sanctified one Shrine every year, on the night of the shortest day, to lure the Sun back. They kept building them after the city's Fall, but those shrines were different. This is one of the originals, still decorated with tiles in a fine cracked blue glaze. The sky above was that colour. You remember it still, even here all these miles of night below.
A pretty place, with a fine scent of the sacred, but cold and rather cramped. You spend the rest of the day sketching the shrine... and find a last offering hidden beneath the circular altar. Treasure, at last!