Rain-over seventy inches a year- keeps the forests of Parc National des Volcans lush and green.  Mountain gorillas live here as do golden monkeys, black-fronted duikers and bushbacks.  Over ninety species of birds frequent the park.  Access to the park is strictly limited to protect the mountain gorillas.  Visitors must register in advance for the guided gorilla tracking hikes and must be at least fifteen years old. Guides are also required for other hikes in the parks.  The most physically challenging hike is to the summit of Karisimbi, Rwanda's highest mountain.  Other hikes in the Virunga Mountains are to the summits of Visoke, Gahinga and Sabyinyo.