The building, which will stand between the Cheesegrater and the Gherkin, will include office and retail space, as well as the now-compulsory viewing gallery over the top two floors (making it the City's highest viewing spot), and a restaurant on the 70th floor with capacity for 200 diners.
Standing at 309.6m tall, the building, designed by Eric Parry Architects, will be within a whisker of the Shard, across the river.
Back in December, when Aroland Holdings unveiled its designs for the skyscraper, Parry said the likes of 1 Undershaft were urgently needed in the City, where office rents have shot up in recent months.
“One Undershaft will create more of the quality office space that is desperately needed in the capital and will reconnect the city’s tall building cluster with the public."
“Most skyscrapers are used Monday to Friday but 1 Undershaft will be used seven days a week, with the public able to enjoy the new public square, viewing platform and restaurant every day. It will be the jewel in the crown of the City of London and something we hope Londoners will be very proud of,” he said.
The company reckons the completed skyscraper will accommodate 10,000 people, with spaces for 1,500 bicycles.