The hub will transform the passenger experience for more than 15mppa and is scheduled to open in 2016.
The 11,000 sq metre Avancorpo extension is being designed by London-based firm The Design Solution.
It will feature new commercial space on two levels with bussing gates below at apron level and includes a walk-through duty free shop.
The extension will feature a new duty-free shop, and passengers will walk the length of the two level galleries before exiting to a new pier or back into the piers in the current terminal.
The retail street has shops on either side has seating in between and at the centre of the building is a 'piazza' with three double height 'icon' shops and a restaurant overlooking the apron.
And the mezzanine has cafes, restaurants and bars and overlooks the apron as well as the 'street' below.
Robbie Gill, director of the project, says: “We have worked on over 100 terminals world wide and this one is going to set a new level of experience for passengers.
"The plan is very simple, with passengers entering at one end and leaving at the other, they will pass every shop on their journey.
“The way-finding is simple, the format clear and most important, it will have a stunning design that has been carried out in a totally contemporary manner but with its roots and materials firmly bedded in the architecture and culture of the city.”
Fulvio Fassone, head of Commercial Services for Aeroporti di Roma, (ADR) says the new building will be the beginning of a new era for retail services at Rome Fiumicino.