Sacré-Cœur, the White Basilica on the Hill

Sacré-Cœur is the first thing most people think of when they think of Montmartre. "Sacré" means sacred and "cœur" means heart, so the name means "Sacred Heart." Notre-Dame is about 700 years old and the Louvre about 800, but this basilica was completed in 1914, around a century ago, which makes it a baby by Paris standards. In 1870, France went to war with Prussia, a kingdom in what is now northern Germany, and lost in 1871. To pull the exhausted country back together and restore the government, people turned increasingly to religion, and they decided to build a great church on Montmartre to soothe their weary hearts. The site was chosen because it was where Saint Denis was beheaded, making it the holiest ground around.

Hagia Sophia in Istanbul served for a long time as a church and later as a mosque. This huge house of worship blends Byzantine and Islamic architecture, including its round dome. Sacré-Cœur also draws on Byzantine architecture, which is why, unlike most churches, it has rounded domes.

Its exterior is unusual too. Most Paris churches are brown or a light earthy color, but this one is strikingly cool white. It's built from limestone quarried at Château-Landon, south of Paris. When rain touches this stone, calcite dissolves out and whitens the surface, so it stays white over time. Look closely at the building and you'll see that the areas under the eaves, which rain rarely reaches, look dark.

The statue at the center of the façade is Christ, placed there because the basilica is dedicated to Jesus. Facing the church, you'll see bronze equestrian statues on either side: on the left is Louis IX, known as Saint Louis, France's holy king, and on the right is Joan of Arc, the hero who saved France. The bronze has oxidized over the years to its present blue-green. In the middle of the entrance, a bronze door is carved with scenes from the life of Jesus, including the Last Supper.

Entry into the basilica is free, so step inside if the line isn't long. Climbing the dome above costs an admission fee. Once you're inside, look up at the ceiling mosaic called France Venerating the Sacred Heart. It's one of the largest mosaics of Christ in the world, at roughly 475 square meters, and was made to praise Christ. Centered on Jesus, it's divided into upper and lower halves: the lower part shows France as it was at the time, and the upper part depicts saints.

If you want a bird's-eye view of Paris, climb the dome. After the Eiffel Tower, it's one of the highest viewpoints in Paris, and on a clear day you can see far across the city.