As a cycling enthusiast, I've always been amazed by how fast professional cyclists can ride downhill. On average, these athletes can reach speeds of 60-70 km/h (37-43 mph) while descending steep mountain roads. The fastest riders can even surpass 100 km/h (62 mph) in certain conditions! Their incredible skills, bike handling, and aerodynamics play a huge role in achieving such speeds. It's thrilling to watch them in action, but remember, they are professionals - so don't try this at home!