Baghdad became a very important city in the early Islamic civilisation.
Caliph Al-Mansur ordered the building of Baghdad between AD762 and AD767.
Baghdad was also known as the Round City because it was built in a circle.
Important buildings like the House of Wisdom and Caliph鈥檚 Palace were in the centre of the city. The House of Wisdom was a huge learning centre where people studied.
The city was world famous as being a centre of learning with libraries and schools.
It even had a hospital.
There were around 1 million people living in Baghdad by AD900.
This made it the largest city in the world at the time.