A lot of the guide books I read spoke of Sagrad Cor as a gaudy, kitsch type of cathedral that wasn't worth much of a visit, but I happened to really like it. We went all the way up to the roof (which I absolutely recommend for amazing views) and thought it was just lovely.
Located in the same hall as the Tibidabo attractions park is church is a big hit. Inside it is very small but outside it looks huge. The most beautiful are the views you have from the city and the valley. You can climb to the high towers but it's payable.
In the mountain of Tibidabo, next to the attractions park, you find this historical style church, which blends several different styles, its construction started in 1902 and its work ended in 1961. It is very beautiful as outside as inside it is and calls attention because when you are on the mountain you see from far. The views of Barcelona from here are amazing. You can get up on bus, your own car or funicular.