Sudwala Caves, Cave system in Mbombela, South Africa.

Sudwala Caves is a cave system in Mbombela that extends deep into the earth through networks of ancient dolomite rock. The passages and chambers within form a complex underground structure accessible to visitors.

The caves formed about 240 million years ago in Precambrian dolomite laid down some 2.8 billion years ago. Stone tools show Stone Age use, and in the 1860s Somquba, brother of Swazi heir Mswati II, sheltered here with his Nguni cattle; Mswati's regiments lit a fire at the entrance, but the cave's airflow defeated it and Abel Erasmus's Lydenburg commando relieved him. In 1900 Boers stored ammunition for their 94-pounder Long Tom guns here, and in 1914 a company dug out bat guano for fertiliser.

The Miriam Makeba Hall within the caves measures 70 meters in diameter and 37 meters in height, hosting musical performances by various artists.

The caves lie in the Mankelekele hills of Mpumalanga, about 35 km from Nelspruit, and are open every day of the year, public holidays included. Day tours last about an hour; a monthly five-hour Crystal Tour goes 2,000 metres in to a chamber with aragonite crystals and the Sudwala Star. The main chamber holds a constant 17 °C, so bring a light layer.

The dolomite holds microbial fossils of a cyanobacterium called collenia, formed about 2 billion years ago, long before the cave itself took shape 240 million years ago. Look for the dark bands in the grey and tan ceiling rock.