Aside from all the main tourist attractions (Prague castle, Charles bridge, and old town square), we highly recommend visiting Vyšehrad if you have time during your stay in Prague. Vyšehrad is a castle on a hill on the South side of the city center. Vyšehrad has a wall surrounding the castle grounds from which you have beautiful views over the Vltava river and city. Within the castle grounds you can find a beautiful neo-Gothic basilica and a large beer garden with views over the city.
Náplavka is the river bank on the South side of the city center that runs from Jiraskovo namesti, all the way down to Vyšehrad. Every Saturday there is a farmers' market that starts at 8 AM (so a nice place to start our wedding day). You can find many different stands with food, drinks, and local goods.
There are tons of beautiful parks in Prague, all with their own unique highlights and all free of charge. Kinského zahrada and Petřínské sady are connected parks with winding paths on the hill from which you can look over the city; Letenská pláň has the best view of the river and as a little bonus has a great beer garden and the Prague metronome (Pražský metronom) with unique history; Královská zahrada and Zahrada Na valech are the gardens attached to the Prague castle with the best views of the city; Valdštejnská zahrada (Wallenstein garden) is kind of hard to find but a beautiful little hidden gem with dripstone walls, amazing architecture and as a bonus there are peacocks freely walking around; Riegrovy Sady has the most beautiful sunset views; Zahrada Ztracenka (the Lost Garden) is a small hidden park not known by many people with beautiful views over the city and interesting sculptures. There are many more parks in Prague so feel free to ask for more recommendations!
Signal festival happens to be planned during the weekend of our wedding and this is a super nice light show festival that happens in the streets of Prague. There will be many places where light shows are projected on buildings such as on the national museum, Vysehrad church and the church on Namesti Miru. Definitely worth checking some of these shows out!!