A HUGE concourse could be built underneath Melbourne’s busiest city block in plans for the Melbourne Metro Rail Link.

The concourse would link Flinders St station to the new CBD South station, underneath the corner of Flinders and Swanston streets.

Details of the proposed plans drafted by the Department of Transport, obtained exclusively by the Herald Sun, show five new stations will be built underground from South Yarra to North Melbourne.

And to help pay for it, 19 buildings along Swanston St could be bought and turned into multistorey towers, ­according to the business case.

An artist’s split-level impression of CBD South station, near Flinders St station.

Buildings adjoining the Young and Jackson pub and RMIT University could be bought and developed with apartments and retail shops.

The business case suggested the building next to Young and Jackson could be turned into a 10-storey tower with an ­entrance to the CBD South station incorporated.

On the corner of Swanston and La Trobe streets, a building opposite RMIT University was earmarked for purchase.

The three-storey building would become a 41-storey tower facing La Trobe St, with 10 storeys facing Swanston St, incorporating an entrance to the CBD North Station.

The business case put the residual land value of the 19 buildings at up to $87 million, in 2011 figures.

Buildings next to RMIT University could be bought and developed with apartments and retail shops.

More detail was also given on the proposed locations of the five stations, with the Arden station recommended for the western end of Queensberry St in North Melbourne.

An urban renewal program around Arden station could see a “spine of commercial, retail and residential along a new major north-south boulevard”.

Up to 6000 new residential dwellings and more than 24,000 jobs could be located in the precinct, which the business case said would include “architecturally significant office buildings that act as the gateway to the Dynon urban activity corridor”.

The Parkville station would be on Grattan St, around the Royal Park intersection, with the option of direct access to the new Victorian Comprehensive Cancer Centre.

It would be accessed from three entrances at a new tram super-stop on Royal Pde.

The proposed tunnel project.

The document said no elm trees would be damaged during construction.

There was also potential for a future north-south tunnel from Clifton Hill in the plans.

The CBD North station would be underneath Swanson St, between La Trobe and Franklin streets, and would connect to the existing concourse of the Melbourne Central station.

The most complex would be the new CBD South station, underneath the intersection of Flinders and Swanston streets, running as far north as ­Collins St.

A huge underground concourse, with extensive retail, would connect it to Flinders St station.

Two main entrances at surface level would be located in City Square and on the western side of Swanston St, opposite St Paul’s Cathedral and next to Young and Jackson.