A three-century-old water mill, set in the old district of Sabandia.
© OpenStreetMap contributors
Also to be found in the old countryside is the renovated centuries-old Spanish Colonial mansion Mansión del Fundador.
The oldest market in the center of the city. It's three blocks away from the main square.
An iron bridge designed by Eiffel for the railway. It has been converted to a pedestrian/bicycle bridge. (The railway now crosses the river over a different bridge a few km to the south.) A technological jewel in Vallecito (10 blocks from main square) and a must for people who love trains and bridges. From the bridge, at golden hour (16:00-17:00), you can get some of the best pictures of the volcanoes and the city.
An Andean Baroque style church, finished in 1698. Like many major colonial-era buildings in Arequipa it's built out of sillar (volcanic rock) with carved façades, though the carvings on this church are some of the most impressive depicting animals, plants, and even elements of Pre-Columbian mythology. Also the side cloisters featuring stone carvings, and the decorated interior of the church are worth a view.
A little off the usual tourist path, in downtown Arequipa. It is not as architecturally interesting as the Convento de Santa Catalina, but some of the paintings and artifacts are stunning.
From May to November the main exhibit is the mummy Dama de Ampato, also known as Juanita. It is close to the main square.