Both the Hilton and the Hilton Garden Inn have officially opened their doors at Frankfurt Airport's integrated office, retail and rail centre - The Squaire.

The opening of the two new hotels mean that in the eastern part of the building there are now 583 rooms available for guests - 249 rooms and suites in the Frankfurt Airport Hilton, and 334 rooms in the Frankfurt Airport Hilton Garden Inn.

The building is currently owned by IVG Immobilien, the German real estate company, which intends to sell the property when it is full and completed.

The 660-metre-long complex on top of the high-speed train station at Frankfurt Airport, is a "complete city under one roof" , which allows business to better connect and get closer to their clients, according to its managing director Christoph Nebl.

New Work City, as it has also been named, has room for 7,000 people to work or live on the premises.

Currently the complex houses the two Hilton hotels, a large KPMG office with 2,500 staff and Lufthansa has rented 18,500sqm, which will see 1,000 additional workers based there.

This brings the occupancy rate of The Squaire to around 82%, Nebl said.

IVG Immobilien said however that for 2012 the goal is a letting status of 95%.

The next large step for the company is the opening of the public car park, The Squaire Parking, which will make the building more accessible with its 2,500 additional parking spaces.

Wolfgang Schäfers, managing director at IVG Immobilien, added: "The opening of the hotels is a crowning conclusion for our opening year 2011.

"With the many office tenants who have moved in, the many catering establishments and businesses which have opened, we have taken a large step forward."