Most part of the churches you can visit without paying by entering through the prayers zone.
Though I really recommend getting into this one "for real", because it's really beautiful. It's not very worked up, it's very ample and simple and it has some funerary monuments (also in an underground corridor, but it's very beautiful).
The back yard is also very beautiful (make sure to go there on a sunny day), and you also have access to a museum (nothing of amazing) and to a chapel.
I recommend it strongly!
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