The Gothic-style Iglesia San Marcos has a threefold claim to fame. First, it was designed by celebrated Parisian engineer Alexandre Gustave Eiffel, before his success with the Eiffel Tower. Second, it was prefabricated in Eiffel’s Paris shop in the 1870s (at the order of the Peruvian president), then shipped right around the world to be assembled on site. Still more curious is the construction itself: the entire church is made of stamped and molded cast iron, coated with paint. That’s everything from its unusually thin walls to its pillars, beams and pointy arches; only the door is wooden. The resulting atmosphere is somewhat mechanical for a house of God, but as a feat of engineering it’s impressive.