My first time "witnessing" this Cathedral, I was sitting at home, wide-eyed, watching Rick Steves tour Prague, and subsequently, touring this Cathedral. I knew then I had to see it in person. It's magnificent and easily one of the most beautiful places you have the opportunity to step into. If you can only step into one church in Prague, make it this one. You will not be disappointed. The interior gives a medieval castle vibe, and is full of art. Take your time to absorb it all, no one is chasing you out. This cathedral is in the Gothic architectural style and its exterior is as impressive as its interior.
Lines to get inside can be long, so make sure you buy your entry ticket (just across the way from the entrance) before getting in line. No ticket. No entry.