The Amboni Caves are the most extensive limestone caves in East Africa. They are found 8 km north of Tanga City 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.

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 limestone caves are formed by a special nature of erosion. According to Mturi, there are three theories which explain the formation of the Amboni Caves. The first theory is known as the vedose process. According to this theory, rainwater 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 rainwater seeps through 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 rainwater 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.

The Amboni caves are believed to be the most extensive limestone caves in East Africa, found in Kiomoni village. The caves, a one and half kilometre stretch, are a fascinating historical site, which were used as hiding places for the locals.

The caves are very dark inside and potentially lethal. All tunnels or chambers are accessible to tourists via a guided tour.

The views of towering formations in the caves are an admiration. Nearly all its tunnels or chambers are accessible to tourists via guided tour. Walking through squeezes while getting treated to views of incredible formations makes the visit well worth it.

The caves have religious significance to the local people who pray and make offerings in one of the shrines. For a section of locals, the caves have been long known as the place to worship to pray for different needs. Chamber number one is used for the prayers, in what many people associate with superstitions. Different items are deposited here during players as ‘gifts that the local villagers offer to the spirits.