The summit of Montmartre, the highest point in the city, boasts the Sacré-Cœur. Contrasting the Gothic churches like Notre-Dame, the Romano-Byzantine architecture is both beautiful inside and out. While outside, take in the panorama of Paris and while inside, marvel at The Apse Mosaic - one of the largest mosaics in the world. The Sacré-Cœur website has instructions on how to download the free audio guide on your phone before your visit which we did not do and wish we had. Also, we would advise to research the well-known (and apparently tried-and-true) scams before traveling to Paris. Overall, very minimal for the duration of our trip but the most evident while visiting Sacré-Cœur.