The word 'castle' to me conjures up an image of a heavily fortified stone building complete with battlements and towers.
There is very little of that about Prague Castle (Pražský hrad). Only on the northern side and at the eastern end are there significant remains of the old fortifications.
Although started in the 9th century, the castle has undergone many phases of building and rebuilding, particularly following the disastrous fire of 1541 which destroyed large parts of the castle.
For information on ticket prices, opening hours, etc. please see the Official Site, detailed below.
Only mentioned in passing on the official site are the Audio Guides. Whilst I can strongly recommend these in themselves, they are very interesting, they also give you priority entry to St Vitus Cathedral. On a freezing cold day in March, they are pretty much an essential.
Katedrála svatého Víta (St Vitus Cathedral)
Even in March there were long queues to get into St Vitus Cathedral (Katedrála svatého Víta), and I was very glad that we had hired some Audio Guides (see above), which allowed us to get straight into the relative warmth of the interior.
Inside, however, things only improved slightly. It's probably just me, but I found the endless succession of tourists rushing from memorial to memorial, taking photos of their wife, husband, partner, or significant other, and then moving on, quite off putting. There seemed to be more peace and reverence down at the Lennon Wall (Lennonova zed') than there was in the cathedral.
Don't get me wrong, it is well worth a visit. Although the nave is 19th century gothic pastiche, the rest of the cathedral was built between 1344 and 1562, and and there is much to see. But personally I'd put your camera away and try to soak up what's left of the atmosphere. Well perhaps you might just allow yourself one photo of the nave.
Zlatá ulička (Golden Lane)
Golden Lane (Zlatá ulicka) in the north-eastern corner of the castle, is a street of tiny houses built into the castle wall. Originally occupied by archers and other tradesmen (possibly goldsmiths, hence the name) it is now entirely given over to souvenir shops.
If truth be told, most of the buildings are modern reconstructions, lending a Disnesque feel to the place.
It would have been nice if one of the interiors, (say No. 20 with its original timber-framed upper floor) had been accessible to visitors and presented with something like the original furnishing. However the needs of commerce have priority.
Accessible from the Bílá vež (White Tower) at one and of the street, is the enclosed wall walk above the shops, with its arrow slits and an impressive display of armour.