Molino de Sabandia is a restored colonial-era mill southeast of Arequipa, set in a greener rural pocket below the volcanoes. Its white sillar stone, arches, water channels, and old machinery make it a pleasant contrast to the city's dense historic centre.
The mill is not huge, but the outing is worthwhile for the setting as much as the building. Combine it with Sabandia and nearby countryside stops if you want a slower half-day outside Arequipa's traffic and plazas.