At the moment, the tallest building in the world is Burj Khalifa in Dubai (UAE). Completed in 2010, the structure is 830 metres tall and has 162 storeys. From 2019, the tallest building in the world is set to be the Kingdom Tower in the Saudi Arabian city of Jeddah. It will be more than a kilometre in height.
Saskia Blank of the Ideas 2020 team answered this question.