Great Zimbabwe was once one of the biggest cities in Africa. Around 18,000 people lived there at its peak. The builders cut perfectly shaped blocks of granite from nearby hills and stacked them into walls without using any cement or mortar at all. The stones simply fit together so neatly that the walls have stood for 800 years.
The most famous part is called the Great Enclosure. It is a huge oval wall, 250 metres around, 11 metres tall and made from nearly a million stone blocks. Inside is a tall, mysterious cone-shaped tower. Nobody is completely sure what the tower was for - some say it was a granary symbol, some say a royal monument. The mystery is part of what makes it special.
Great Zimbabwe was a trading city. Archaeologists have dug up Chinese pottery, Persian glass and shells from the Indian Ocean inside its walls. That means people from this stone city in the middle of Africa were trading with merchants from China, Arabia and India hundreds of years ago.
On the city's walls, builders left carvings of soapstone birds. One of these birds is now a national symbol - it appears on the Zimbabwean flag. So the country today carries the name of the city and the picture of one of its carvings, all from a place built nearly a thousand years ago.