For me, the highlight is the parade starting above the castle. Everyone meets up at the Black Ox pub (U Černého Vola) in Loretánské Namesti, and enjoys an hour or two of drinking and music before the parade begins to wend its way down towards the castle and into Mala Strana.
With the Carnival king and queen leading the way (alongside a mounted police escort), closely followed by a throng of revellers in a huge array of different costumes, the parade slowly heads through Hradčanské Namesti, down Nerudova and across Malostranské Namesti towards the Charles Bridge and then into Na Kampé for the real party to start.
Some of the costumes are incredible while others are a bit more makeshift, and many represent the pagan origins of the festival; devils and evil spirits decked in chains walk side by side with pirates and animals (and even someone a bit more sinister!)
The atmosphere is tremendous, and it is impossible not to become immersed in the proceedings. Alcohol clearly plays its part and there are usually plenty of folk more than happy to share their grog with the crowd. A drop of apricot brandy does wonders to hold off the February chill!
Last year, the day was made even more interesting with two demonstrations taking place at the same time and in the same part of town - one pro-immigration and one anti-immigration. To our great amusement, the police redirected both groups away from the parade and settled them into a smaller square until we'd gone past. Fortunately, neither group wanted to resort to fisticuffs that day!
Similar parades and activities take place in Žižkov and Vyšehrad as well as other parts of the city, but for me, this is one of the ultimate Prague Moments - and sadly this year I'm going to miss it as I'm not back in town until two days after the event.