Foster + Partners has won a competition to create a chain of seven stations along an extension of the Sydney Metro, which will tunnel beneath the city's harbour.

Norman Foster's London-based practice will design stations at Crows Nest, Victoria Cross, Martin Place, Pitt Street, Waterloo and Barangaroo – where fellow London architects Rogers Stirk Harbour + Partners has just completed a trio of skyscrapers.

The stations will extend the Sydney Metro northwest, under Sydney Harbour and past the Jørn Utzon-designed Opera House to the city's central business district.

It is part of a wider overhaul of the city's transport system, which will see 66 kilometres of track added by 2024.

"Sydney Metro is Australia's biggest transport project – 31 stations and 66 kilometres of new metro rail for Australia's biggest city," said a spokesperson for Transport for NSW. "It includes the delivery of seven new metro stations across North Sydney and the Sydney CBD."

Foster + Partners has teamed up with consultants Arcadis, Mott McDonald, WT Partnership and McKenzie Group Consulting, as well as engineers Robert Bird Group and architects Architectus for the project.

Construction work is expected to begin on the stations in early 2021. It will complete the following year, in time for the line to become fully operational by 2024.

Foster + Partners and its figurehead Norman Foster ranked highly in the inaugural Dezeen Hot List, as the 10th most read-about architects last year.

The firm is currently working on an array of projects across the globe, including a tower complex at Mecca, a monkey enclosure at London Zoo and Apple's Californian campus, which is expected to open next month.