Ol Doinyo Lengai, meaning 'Mountain of God' in the Maasai language, is a unique and active stratovolcano located in the Gregory Rift, south of Lake Natron in Tanzania. It is the only volcano in the world to erupt natrocarbonatite lava, a type of lava that is black when erupted but weathers to a striking grey-white color. Its distinctive conical shape makes it a prominent landmark in the Tanzanian landscape. This guide explores everything you need to know for a visit, from climbing expeditions to the geological wonders and cultural significance of this sacred mountain. Planning for 2026 and 2027 trips is detailed, offering insights into the best times to visit, trekking routes, and what to expect from an adventure with Top Guide Adventures.