The Roman aqueduct

One of the best-preserved Roman structures anywhere, and it is not in a museum or on an archaeological site — it runs straight through the middle of a working city, over a square, with cafés underneath it. A hundred and sixty-seven arches of granite, stacked dry without mortar, standing since the first century.

The scale is what photographs. Stand people at the base of the tallest section in the Plaza del Azoguejo and the arches disappear upward out of frame; step back to the stairs beside it and you get the whole run receding into the town.

Granite is grey and takes warm light beautifully at the ends of the day, and does very little at noon.