Hells Gate is a mellow little park with incredible geology near Lake Naivasha. A great thing about the park is that you can hike around on foot. There are few to no major predators here, which is actually good, because its one of the few parks where you have the feeling of being very close to the wildlife, unprotected by a vehicle. It gives you a genuine experience and you can have several days of fun in this park.
From Naivasha town, take a matatu to the lake. Just tell the tout to let you off at the turn-of to Hells Gate. Its before Fishermans Camp. From the sign posted turn-off its 2 km to Elsa Gate. The entry fee is relatively cheap, and so is the camping fee.
Attractions include Fischers Tower, Central Tower, Obsidian Caves, Ol Karia Geothermal Station, and the Hells Gate Gorge. Its a long walk from Elsa Gate to Central Tower at the end of the park and back, so you may want to stay the night and explore the following morning. There are 3 major camp sites not far from Elsa Gate. If you enjoy technical mountain climbing, you can do it here. Also, if you want to explore the park by mountain bike, ask the people at Fishermans Camp where you can rent them.