We visited on a Wednesday at 3:00pm. It was very busy like we expected given it was a pretty sunny day and a popular attraction. It’s a beautiful Catholic Church, construction began in 1875, completed in 1914. We waited in line about 20 min to go through security to get in. The inside is beautiful and free to see. To get to the dome, you need to go back outside, and down the steps on the left side of the church. 7 euros per person, purchased tickets on site, only a few people in front of us so waited just a few minutes. 300 stairs to the top (no lift). A tight fit in many places and not good if you get claustrophobic, but once up the views are amazing. We spent about 1.5 hours there. Also there were people selling ice cold bottled water/soda around the outside of the church (1 euro/water, 2euro/soda, cash only). Taxis available at the foot of the outdoor steps. It was definitely worth seeing!