This a beautiful area its a lot of walking up hill to get here from the metro. But once you make it to the steps to the Basilica you will realize it was well worth it. The Basilica is free to enter, remember to take off your hat and stay quiet. Inside the Basilica is a breathtaking, it's really incredible how large it really is. If you decide to go to the dome you have to go down the left side stairs outsideof the Basilica to the kiosk- the cost for Adults is 7€ at the Ticket machine and you can get kids admission for 4€ at the cash desk inside the door, both my kids 10 and 13 were considered kids. --HUGE DISCLAIMER-- the stairs to the top are very tight and if you are claustrphobic & tall I'm 6'3" you may want to skip this attraction. Also if you are not able to do stairs and a lot of them stay away. Its a total of 600 stairs 300 up 300 down. Understand that those 300 total steps to the top you will be rushed by people behind you to get to the top. It is exausting so prepare yourself for a long and grueling hike upwards to the top. You can't stop and let others pass you as the stairway is very small. Once you get to the top though, the views are incredible of all of Paris. Take your time and sit on the benches and take it all in while you catch your breath. I'd almost say the view is worth the trip up, but I would never do that climb again. When you are finished taking in the spectacular views its time to go down. Some advice wait till the most athletic people depart then head down. There are a few spots where you are able to let people pass at the top areas but then once you enter the "tube" its on you to descend at a pace that works with those behind you. The Basilica is a must, just for the views alone you can achieve those great views by standing on top the stepsleading into the Basilica. If you feel adventurous head up to the dome for more amazing views and pictures.