If my heart took the form of a structure, it would closely resemble the Sacré-Cœur. The Eiffel Tower may be the star of Paris, however the Sacré-Coeur (to me) is a close second. I love the Roman-Byzantine influence of the basilica-it's curves, symmetry, and striking white stone. It is a bit of a climb to reach the Sacré-Coeur, but it is absolutely worth the view when you get there.
Montmartre