Construction work on the world’s first 1km-high building, the Kingdom Tower in Saudi Arabia, is set to begin on April 27.

The $1.2 billion project has been plagued by setbacks since it was first proposed in 2011, but above-ground work on the Jeddah super skyscraper will commence next month, Building reports.

Stretching at least 1,000m, the slender structure will be more than three times bigger than Europe’s tallest building, The Shard, and will overtake the 828m Burj Khalifa in Dubai to become the tallest building in the world.

The skyscraper will be a mixed-use building featuring a luxury hotel, office space, luxury apartments and the world’s highest observatory. The complex will contain 59 elevators, including five double-deck elevators.

Designed by Adrian Smith + Gordon Gill Architecture, the tower is slated to reach completion over a timescale of 63 months. Foundation work began in December 2013.

The original design was for the building to reach 1.6 km — just under one mile. However, the plans have since been revised and though the client, Jeddah Economic Company, has yet to confirm the exact measurement, it is likely to be closer to 1 km, according to Building.