The lower photo is the crypt, where they have been offering mass for years now, awaiting the opening of the upper church. I was looking for photos of the new upper church, but all I found was a short video of the Pope right at the altar, so I couldn’t really tell what it looks like. All I could see were the organ pipes (it seems to have a very impressive organ, I have to look up the maker).
Supposedly, however, the roof is an enameled leaf-like pattern with glass set into it. I have to go to Barcelona and see it now!