Is it must for the trekking to be organized by the Company?
Oh, I am sorry, I haven't seen you question until now. I hope my answer is not going to be too late. You don't need a company but it is wise to go with a local guide. People from the Maasai Giraffe Ecolodge, where we stayed, went with local Maasai working at the lodge
Honestly, I can't imagine how we would have found the trailhead without a guide. Once on the trail, it's obvious and you will not get lost.
it can be organized by company or youself
The cost to climb Ol Doninyo is 100 USD and the community there at the village will give you a guide to come with you. It takes more than 5 hours to reach the summit and the ascend starts around midnight.
It is not easy to go to the village by your own because the distance from Arusha is around 400 Km and I think there are no buses going there.So, it is better to make a deal with a company.
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