Good quality roads, well indicated directions, very nice nature, the circuits will take you to at least one mediaeval castle, residence of probably the richest Czech entrepreneur and enough pubs, kiosks and shops (open even during the weekend) for those who may need additional hydration or desperate for some carbs. Most of the year you meet quite a number of mountain and road bikers, solitary or in groups. Cars are few and the drivers respect the cyclists.
You can reach main starting point in Hostivice by car from Prague (there are two big parkings) and also by underground (terminal station line B – Zličín). Obviously you can bike directly from Prague, too. In this case probably the easiest is to keep straight on Plzenska street from Andel (9km steadily uphill, though the road - unless early morning and/or weekends, is quite busy). Don’t forget to turn right to Hrozenkovska street once Plzenska becomes Na Radosti and follow the road to Hostivice. Over there start looking for dedicated yellow indications with distinctive blue/white/green/black logo of the Circuits (Krivoklatske Okruhy T1-T8). The circuits are from 18km to 90km, elevation gain from 105m to 1,245m. So when planning to ride from Prague, add at least 20km on a top of what the guide says for one of the circuits.
Just beware of the roe deers crossing the roads. They are frequent, big and don’t respect the traffic rules…One can easily ruffle your hair...