Aso Rock is what is called a 'monolith' - a single, enormous piece of stone. It was made over millions of years, as the softer ground around it slowly wore away with rain and wind, leaving the very hard granite behind. It is 400 metres tall - higher than the Eiffel Tower in Paris.
The name 'Aso' comes from a word in the Asokoro people's language, meaning 'victorious'. Long before Abuja was built, the Asokoro and other communities lived around the rock and treated it as a special place. Today its name lives on in 'Aso Rock' itself, in the neighbourhood Asokoro, and in the government buildings clustered at its base.
Abuja - the city around Aso Rock - is Nigeria's capital. It is not the country's biggest city (that's Lagos), but it is where the country's leaders work and meet. Abuja was specially designed and built in the 1980s and 90s, and Aso Rock was kept as the heart of the new city.
From the top of Aso Rock, you can see the city of Abuja spread out below: wide roads, tall buildings, parks and another smaller rock formation called Zuma Rock in the distance. Most visitors don't climb it - it is steep and the top is reserved - but it is one of the most photographed places in Nigeria.