What's actually inside
"Prague Castle" isn't one building, it's a fortified complex on top of Hradčany hill that's been the seat of Czech power since the 9th century, and today holds the official residence of the President of the Czech Republic alongside its historic sights. The big draw at its centre is St Vitus Cathedral, a soaring Gothic cathedral whose spires you can pick out from most of the city — step inside for the stained glass, including a famous window designed by Art Nouveau painter Alfons Mucha.
Beyond the cathedral, the complex holds the Old Royal Palace, the Basilica of St George, and Golden Lane — a row of tiny, colourful historic houses built into the castle walls, once home to castle workers and (according to the best-known legend) alchemists.
Free vs. paid
Walking the castle courtyards and the exterior of St Vitus Cathedral costs nothing, which is why so many visitors come up just for the views and the changing of the guard. Seeing inside the cathedral's main nave, the Old Royal Palace and Golden Lane properly requires a paid ticket, usually sold as a choice of circuits covering different combinations of interiors — decide before you queue which one you actually want, since not every circuit includes every building.
Changing of the Guard
Guards change at the main gate every hour, but the fuller ceremony with a small brass fanfare happens at noon — worth timing your arrival around if you want the photo without the rest of the crowd's photos in it.
Getting there and getting around it
Most people arrive via tram or a walk up from Malá Strana, or the metro to Malostranská followed by a short tram ride or a steeper walk. Whichever way you come up, plan to go back down through Malá Strana — the walk downhill through its lanes is one of the best parts of a castle visit, not just a way to get back to the river.
How much time to give it
Treat this as a half-day minimum. The complex is large, the queues for the cathedral and popular interiors build through the morning, and rushing it tends to mean you see the outside of everything and the inside of nothing.