Mount Meru situated east of the Great Rift Valley and about 40 km southwest of Kilimanjaro in northern Tanzania's Arusha National Park, is considered an active volcano and is the country's second highest mountain.
Mount Meru is also considered the fourth highest mountain in all of Africa by some (after Kilimanjaro, Mount Kenya, and the Rwenzoris - aka the Mountains of the Moon). 500,000+ years ago, Mount Meru erupted in a tremendous explosion that destroyed it's cone shape and resulted in a horseshoe crater with the eastern side removed. The resulting mountain has its summit on the west side with its inner walls rising over 1,500m from the crater floor, making them among the tallest cliffs in Africa. In the past 100 years, eruptions have been reported as the Ash Cone continues to build inside the crater. The first ascent is still in dispute and credited to either Carl Uhlig in 1901 or Fritz Jaeger in 1904.
Although this is a spectacular mountain with amazing scenery and wildlife, it's a location in East Africa means that most international visitors will visit Mount Meru as a secondary trip in conjunction with their primary destination, usually Kilimanjaro, Mount Kenya, or the Ngorongoro Crater.
Reasons to do this summit include: (1) amazing views into the summit crater and ash cone, (2) hiking along the crest of the crater rim, (3) nice, but distant, views of Kilimanjaro from the summit, (4) the ability to see a lot of wildlife on the lower slopes in the form of a walking safari, (5) the chance to escape the tourist crowds, and (6) for Americans, the ability to summit another peak taller than Mount Whitney. Arusha National Park provides certificates for people who submit the Little Meru sub-peak (3,820 m / 12,533 ft) or Socialist Peak - aka the Mount Meru summit.
Although the name Socialist Peak is listed on the summit certificate, this name was rarely used and given that the Tanzanian government is moving more towards capitalism, it will probably never be more than a curiosity.
The 14 km (8.7 mi) or 19 km (11.8 mi) YDS class 2 Momella Route is the primary and only official route to the summit today. This route starts at the Momella Gate (1,500 m / 4,921 ft) and uses one of two tracks to Miriakamba Hut (2,514 m / 8,250 ft), either a shorter 5 km YDS class 1 route or a longer 10 km YDS class 1 route that allows one to see more wildlife, scenery including waterfalls, and old huts. From the Miriakamba Hut, you take a 4 km YDS class 1 trail through some forests up to the Saddle Hut (3,566 m / 11,700 ft). From Saddle Hut, you can either summit Little Meru (3,820 m / 12,533 ft) or follow the route another 5 km YDS class 2 to the Mount Meru Summit, aka Socialist Peak.
On the way up to the summit from Saddle Hut, the first notable bald area you'll reach is Rhino Point where you can get amazing views of the summit and the inner crater walls, providing there are no clouds. You'll know you are at Rhino Point because there is a pile of bones in the center of the clearing. The easy YDS class 2 portion of the hike involves crossing two moderately long low-angle rock slabs above Rhino Point. Also from Rhino Point to the summit, there are green blazes and arrows painted on the rocks to show you the way, however, these can be hard to see at night. There is a metal flag of the United Republic of Tanzania on the summit as well as a wood box and summit register.
Before Mount Meru was included in Arusha National Park in 1967 it was also possible to reach the summit via the North and West Slopes, however, use of these trails to enter the park (and reach the summit) is now illegal. It is, however, legal to climb the inner Ash Cone but the park only recommends this for researchers and issues a special permit for this activity.