The Burj Khalifa has 163 floors that people use, plus extra service floors above. Inside, there are homes, offices, a hotel and viewing decks where visitors look out over the desert and the sea. The lifts are some of the fastest in the world - they zoom up the building at around 10 metres every second.
Building it was a huge challenge. The desert ground is sandy, so engineers had to drill deep concrete piles into the earth - over 50 metres down - before the building could even start growing upwards. The tower stands on a base shaped like a three-petal flower, copied from a desert wildflower called the Hymenocallis. That shape helps it stay steady when the wind pushes against it.
The outside is wrapped in 26,000 panels of glass, each one cleaned by special teams who climb the sides on ropes. From a long way away, the building can look like it is changing colour - that is the sunlight bouncing off all that glass.
Because the Burj Khalifa is so tall, the sun sets at the top a few minutes after it sets at the bottom. During the month of Ramadan, people who live high up sometimes wait a little longer than people on the ground for the evening meal to begin.