Brussels has many beautiful churches, but the largest of them all is the Basilica of the Sacred Heart . This is said to be the fifth largest church in the entire world, 89 meters high and 167 meters long. The first stone of the church was laid down in 1905 and the church was finalised in 1971. As you probably understand this is a very modern church, built in Art Deco style. As you visit the church do not expect a beautiful church such as many other churches in Brussels, rather expect something modern and a bit different.
The basilica has free entrance, so you should definitely come by. It is possible to visit the tower of the church from where you can enjoy a beautiful view of Brussels. Just as good as the view from Atomium, but much cheaper.
If you travel to the Basilica of the Sacred Heart you can travel with metro to Simonis. From there you can have a nice walk throughout a park, and in the end of the park you will see the church.