The Amboni Caves are the most extensive limestone caves in East Africa. They are located 8 km north of Tanga City in Tanzania off the Tanga-Mombasa road. The caves were formed about 150 million years ago during the Jurassic age. It covers an area of 234 km². According to researchers the area was under water some 20 million years ago. There are altogether ten caves but only one is used for guided tours.
Amboni Limited, a company which was then operating sisal plantations in Tanga Region acquired the area in 1892. The company notified the British colonial government about the caves who in turn declared the caves a conservation area in 1922.
It is not known when the caves were exactly discovered but reports indicate that ethnic groups such as the Segeju, Sambaa, Bondei and Digo who lived near the caves used it for prayers. In 1963, the then government of Tanganyika handed over the caves to the Department of Antiquities.
These caves have been subject of local legends and a number of mythical and awe-inspiring stories have been attributed to the caves. To the local people the caves are regarded as supernatural formations where supernatural powers commonly known as “Mizimu” are believed to have been residing since the caves formation. There are chambers treated as sacred chambers for worshiping some spirits. One of them is called “Mzimu wa Mabuvu”. Some believe that there is a powerful deity which can alleviate their sickness, sufferings or increase their fertility.
These limestone caves are formed by a special nature of erosion. According to Mturi (1975:18-19), there are tree theories which explain the formation of the Amboni Caves. The first theory is known as the vedose process. According to this theory, rain water absorbs carbon dioxide in the atmosphere and forms a weak carbonic acid which is capable of dissolving calcium carbonate minerals of which limestone is formed. When this acidulated rain water seeps trough the limestone it is dissolved and cavities and caves are formed.
The second theory is that of phreatic origin. According to this theory, the caves are formed by erosion from the sub water table. The rain water with carbonic acid rapidly seeps through the limestone and reaches the water table before being a saturated solution of calcium bicarbonate. At this stage it is still capable of acting as a dissolving agent for the calcium carbonate.
Access is by road from the Tanga – Mombasa road. For access to the main forest block (Msitu wa Mbogo) turn left 5km after Tanga onto the B121 road to Mjessani. Park the vehicle 5.5 km along this road and walk south along paths for 2 km to reach the river. For access to Amboni Caves forest patches take the left turning to Kiomono village 4 km after leaving Tanga on the main road to Mombasa. The road runs through the village and down to the caves. Park and proceed on foot along the river to reach the other forest patches further up-river.
All sites can be reached directly from Tanga by foot within two hours.