Like I always said elsewhere, this is one biggest church in you can get into for nothing in Prague which is saying a lot. You need to be savvy for the free entry, one of those being to come in via the police stop at the park end during the afternoon. You won't get up the front but you will gain a beautiful view of everything from inside at the rear. It is magnificent, honestly. Then aim at the cathedral and you should eventually be able to join the free queue. And I've seen a few cathedrals. The artwork is slavic in the style of Mucha etc, and the glass windows tell us why glass work is still big time in Czech.
This beautiful church adds glamour to the Prague Castle. I think it's always mistaken as the castle itself. The stained walls of this church are appealing that make it more charming. The interiors are superb - you'd appreciate it stood the test of time. From a distance, it's Gothic architecture is unmissable.