I’ve been to Prague several times, all the things mentioned above are great. Charles Bridge is worth waking up super early for - if you go just before sunrise is gorgeous... and even then, there’s people, but not nearly as many as let’s say an hour later. The castle is cool, but there’s a lot to see. I like to just walk around Prague in the morning, the city is really cool and has a nice atmosphere... until you encounter some Czech people. I find them unbelievably rude. They do not care. 8 out of 10 experiences from pubs/restaurants/shops etc are really bad. I’ve been to various places in Czech and from what I’ve been told - even Czech people don’t like Czech people from Prague. Maybe it’s the capital city thing but my god they are rude. So, don’t be bothered if somebody is really unpleasant .
I once got asked to leave the pub because I didn’t order enough!
Anyway, I didn’t see anyone mentioning Petrin tower. If you go there at sunset and the weather is good - the view from there is incredible. Nice to walk up there through the park. It’s on the hill, where Strahov Stadium is.
Here’s a photo taken at Charles Bridge last Easter at sunrise.
Enjoy your stay!