The Sacré-Cœur, a brilliant white church, stands high above the northern part of Paris. Its white towers and onion-shaped dome, rising 83 meters into the sky, are visible from many places across the city. Construction began in 1875 and continued until 1914. The site was chosen because it was the birthplace of La Commune, and the church was officially built as an act of repentance for the violence during the civil war. Thousands of Communards were executed here, and the church also serves as a memorial for those lost in the Franco-Prussian War of 1870. Wealthy businessmen funded the project, and several architects worked together to design the church's unique Romano-Byzantine style. Sacré-Cœur was finally consecrated in 1919.
Sacré-Cœur offers some of the best panoramic views of Paris. From the dome and the square in front of the church, visitors can look out over the city, sometimes as far as 50 kilometers on a clear day. This viewpoint, located 200 meters above sea level, is only rivaled by the Eiffel Tower. Energetic visitors can reach the top of the hill by climbing stairs from different directions. For those who prefer an easier route, a funicular railway travels frequently up and down the hill from Place St. Pierre. Signs for "Funiculaire De Montmartre" guide the way.
Inside the church, photography is strictly forbidden. Guards are quick to enforce this rule, and anyone seen taking pictures may be asked to stop and could be chased by staff.
On the lower steps leading up to Sacré-Cœur, groups of young men may approach visitors, offering to tie a small string around a finger, sometimes claiming it is for the church. It is best to avoid engaging with them. If approached, gently pull your hand back and continue walking. If a situation feels uncomfortable, raising your voice and asking for help can attract attention and encourage others to assist or contact the police.
Source - https://en.wikipedia.org/wiki/Sacr%C3%A9-C%C5%93ur,_Paris