Mount Longonot is a dormant stratovolcano standing on the floor of the Rift Valley near Naivasha, two hours from Nairobi. The trail up is short, steep and almost entirely unshaded, on loose volcanic soil, and it brings you to the crater rim at around 2,600 metres, where the whole caldera opens up beneath you: a forested floor roughly eight kilometres around, completely enclosed.
Most people stop at the rim, and that is a perfectly good day. The full circuit of the rim adds another three to four hours over a run of steep peaks and saddles, takes in the true summit, and on a clear day gives you Lake Naivasha, Hell’s Gate and the Aberdares. Come with proper shoes and more water than you think you need. Park entrance fees, transfers from Nairobi, drinking water and a guide are included.