World's Tallest Tower: Arabian Race to the Top

Which is going to be the world's tallest building? Why is there any other?

On April 1, 2013, the Jeddah Tower (formerly, Kingdom Tower) commenced construction in the Kingdom of Saudi Arabia. The original planned height was 1 mile. But due to geological restraint in the area it was reduced to 1 km, still surpassing the Burj Kalifa (828 m). It has a budget of US$1.23 Billion which is expected to complete by 2020.