The majestic facade of this enormous edifice looms over an entire neighborhood. Construction started in the 17th century over the remains of a medieval church; it took over 100 years to build, and one of the towers was never finished. Inside, the cavernous interior seems to command you to be silent; several important works of art are tucked into the chapels that line the church. The most famous of them are three masterpieces by Eugène Delacroix: Jacob Wrestling with the Angel, Heliodorus Driven from the Temple, and St-Michael Vanquishing the Devil (on the right just after you enter the church). Jean-Baptiste Pigalle’s statue of the Virgin and Child lights up the Chapelle de la Vierge at the farthest most point from the entrance. A bronze line runs north–south along the floor; this is part of a gnomon, an astronomical device set up in the 17th century to calculate the position of the sun in the sky. A small hole in one of the stained-glass windows creates a spot of light on the floor; every day at noon it hits the line in a different spot, climbing up to the top of an obelisk and lighting a gold disk at the winter equinox. Because of their size, churches were an ideal spot for this type of measurement, making for a rare collaboration between science and religion.