What is Prague Castle
Let's start from the fact that Prague Castle is not a castle. This historically established name is an imprecise translation of the Czech word "hrad", which has a wider meaning. In fact, this was a fortified seat of the kings, with everything appropriate: churches, noblemen palaces, seats of secular and religious authorities. It was expanding over time and now, being 570m long and 128m wide, it is considered 2nd biggest world castle after Polish Malbork (or the biggest one - depends on how you measure).
It sits on a hill on the left bank of Vltava river (opposite to the Old Town) above the ancient Mala Strana (Lesser Quarter) district. What people believe to be Prague Castle though, which dominates the Prague cityscape and can be easily seen from anywhere, is just St. Vitus cathedral - the central building of the castle. Despite being on the top of the hill, it is not the highest point in Prague - hilly left bank continues climbing up for miles from the river.
Prague Castle history
The history of the castle begins in the 9th century AD, when the rulers of the neighboring tribes first settled on the hill above Vltava. It was just a fortified settlement at that time, one of many. In the 10th century though Prague Castle established itself as a major stronghold - on the one hand, its rulers conquered concurrent tribes and became kings of Bohemia; on the other hand, they concluded a union with (or accepted the dominance of) the powerful Kingdom of the East Franks. It also established itself as a major religious place: the first convent appeared here in Bohemia, the first church in Prague (St. George Basilica), and first relics of a saint - King Wenceslas, who later became a saint, brought relics of St Vitus and founded a chapel, which became over centuries the St Vitus Cathedral.
In medieval times, it was serving as a seat of kings of Bohemia and its fate was quite similar to other feudal castles: every 10 or 20 years it was besieged by some relative of the acting king, claiming the full power. The period of wars stopped with the coronation of Charles IV, the most eminent Bohemian ruler. Besides being the king of Bohemia, he was elected the Emperor of the Holy Roman Empire, so, in fact, the second most important person in Europe after the Pope. He initiated a lot of construction everywhere, and one of his most important projects was St Vitus cathedral. As we see it now, the cathedral started in 1344 and was finished in 1929 (yes, 600 years after). He also built a king's palace on the grounds of the castle (actually, the absence of suitable accommodation for the king had troubled the castle throughout most of its history and was one of the reasons why Prague lost its importance over centuries).
Next series of construction works in the Castle and around were carried out in the late 16th century by the first Habsburgs on the Bohemian throne, Ferdinand I, Maximilian II and Rudolf II. The castle was extended, and new representative palaces appeared on its eastern side. Castle gardens in Renaissance style were created instead of vineyards. At the time of Rudolf, who chose Prague as his main seat, the castle hosted an exquisite collection of art objects and was a centre of scientific research — by the standards of the time. For example, one of the first telescopes was delivered from Italy to the court of Rudolf.
Turbulent political events that followed devastated most of richness of the castle interiors. First, Protestants destroyed the interiors of St Vitus Cathedral. Then, since emperors lived no more in the castle, the collection of Rudolf dispersed over time - some remnants of it ended up being thrown out into the Deer Moat - ancient fortification around the castle - under the enlightened absolutism of Joseph II.
Only with the declaration of independent Czechoslovakia the Prague Castle became again the seat of the state head, now president. Which it is now - it is the official seat of the President of Czech Republic.
Inside Prague Castle
As mentioned, the castle is a complex of many buildings, about 50. Below are the most noteworthy:
St Vitus Cathedral
Formally called the Cathedral of St Vitus, St Wenceslas and St Adalbert, it is the main catholic church of the country, respectively, the cathedral of the archbishop of Prague. The construction of the current building began in 1344 by the order of Charles IV. The first architect was Frenchman Mathieu d'Arras, but after his death Charles' favorite architect Petr Parler took over. Under the guidance of Petr Parler only the rear part of the cathedral and the bell tower were completed. The rest was suspended until the year 1873, when the works restarted and were completed in the year 1929. So the facade of the cathedral, where most tourists stop, is younger than Empire State building, and, though big, nothing extraordinary for its time.
Though the old entrance, below the bell tower, is decorated by an outstanding mosaic of the Last Judgment, unique on a world scale. Inside the cathedral, there is a richly decorated gothic St Wenceslas chapel, which also serves as entrance to the cell keeping Bohemian Coronation treasures (not available for display). The Cathedral serves as the last resting place for numerous Bohemian kings, including St Wenceslas, Charles IV, Rudolf II and many others. Richly decorated silver baroque tomb of St John of Nepomuk is also there. Lastly, stained glass windows for neogothic part of the cathedral were created by the foremost Czech artist of that time - Alfons Mucha, Max Svabinsky and others.
St George Basilica
Basilica of St George is the oldest existing church in Prague, founded in 920. Besides its baroque facade, it kept its Romanesque character from the year 1142, even with some wall paintings remaining.
Old Royal Palace
The Old Royal Palace dates back to the beginnings of the Prague Castle, that is, to the 10th century. It was extended and rebuilt numerous times, and its present shape was almost finalized in the year 1502 with completion of the main hall by king Vladislaus II of Hungary (who was actually a Pole and ruled Czechia). Besides its architecture, it has a historical importance: here, with the defenestration (throwing out of the window) of the Habsburg representatives, started the Thirty-years war, which devastated a substantial part of Europe (mostly Germany) and led to the reinforcement of Catholic church.
Lobkowicz Palace
A renaissance palace, owned by Lobkowicz family since 17th century, displays ornate interiors and has several interesting collections, including a small but impressive collection of paintings and a collection of late medieval arms.
Prague Castle tickets, opening hours and tours
The Castle itself is accessible to the general public every day from 6 am to 10 pm free of charge. Access to the interiors has a more complex structure: accessible buildings are divided into 2 circuits - circuit I (essential, like St Vitus or St George) and circuit II (I would call it supplementary). Ticket price for circuit I is roughly 18 Euros, for circuit II - 14 Euros (you'll need to pay Czech crowns). Tickets to belfry are separate. Lobkowicz palace, as a private institution, has its own tickets (~16 Euros) and sales points. All the tickets can be purchased on place (expect to spend some time in line), and audio guides and live guides in various languages are available too.
Interiors are accessible from 9 am to 5 pm in summer and from 9 am to 4 pm in winter.
For complete up-to-date information refer to the official website.
There are several entrances to the castle area, the safest way is to take tram 22 to the stop Pražský hrad (Prague Castle) and follow the crowd.
Overall
Prague Castle is definitely a place not to miss in Prague. It bears layers of history. But if you just go there, you'll miss most of it. Make some research beforehand and go not just looking around, but looking for history. On the other hand, it's overhyped. It's jammed by tourists which stare at the St Vitus facade, shuffle through Golden Lane and observe the President guard shift. And miss all the history. While St Vitus is definitely a place to see - but not the facade - the Golden Lane has its non-commercial counterpart, called New World, which is rated as top "hidden gem", just 10 minutes walk away.
I do not have a dedicated tour for Prague Castle, but we make a stop to look at the exteriors and talk about the history during the Historical Walk, and I can include a more detailed visit in custom tour.