This is one of the most difficult rides on the planet. The Mauna Kea Access Road goes from Saddle Road up to the observatories. This is a steep winding road with some sharp switch backs with a total elevation gain of over 7,000 feet. Due to the danger of altitude sickness and the possibility of rapidly changing weather (including strong winds, rain and even snow) it is not recommend to attempt this climb without support. Visitor's are advised to stop at the Information Station to get acclimated to the altitude before going on. This is also the only place to refill water. Shortly after the Information Station a gravel section of a little over 4 miles starts. A mountain bike or cross bike with knobby tires will be essential for climbing above the visitor's center. Here there are some spots when you need to get off your bike and walk. After the gravel section ends, it's around 3.5 miles to the summit. At the top you enjoy a 360 degree view. Many people opt to forgo the bike down and instead ride down with a support vehicle.