Dutch designers UNStudio and German practice HPP Architects have joined forces to deliver four skyscrapers and a new urban quarter in the heart of Frankfurt.

In 2015, development firm Groß & Partner acquired a 16,000sq m (172,200sq ft) plot on Junghofstraße, which had been inaccessible for nearly half a century. UNStudio won the architecture competition for the project, called FOUR Frankfurt, the following year.

HPP have now been added to the design team as part of a new joint venture, UNS + HPP, that has established an office in the city.

Together, the firms will develop plans for two office towers and two residential towers, reaching heights of 228m (748ft). The quartet will sit atop a vast plinth housing hotels, restaurants, bars, shops and open public spaces.

New renderings have been released illustrating how the project aims to bring together “a mix of work, living, relaxation and recreation”, with pathways, passages and accessible rooftops connecting spaces across the quarter, and the heritage-listed facades of existing buildings incorporated into the otherwise futuristic design.

“FOUR Frankfurt will be built, first and foremost, for the people of Frankfurt,” said UNStudio founder Ben van Berkel. “It will not only add to the city’s skyline, but also to the liveliness of Frankfurt as a whole.

“A development with this level of urban effect is particularly timely, as Frankfurt is currently taking up an even bigger role on the European stage. To play a role in this urban transition is a fantastic opportunity for UNStudio and our new consortium partners HPP.”

Werner Sübai, responsible partner at HPP, added: "UNStudio and HPP bring to the scheme many years of experience working on major projects, as well as a combined expertise in design, BIM-based planning processes and complex execution."

Four Frankfurt is expected to be completed in 2023.

UNStudio have become well known for their large-scale, leisure-infused projects, including a pair of sinuous towers in Hangzhou and a diamond-patterned destination for shopping, strolling and socialising in Shanghai. They are currently working on a major mixed-use tower complex in Melbourne and one of the largest urban projects in Western Europe: the redevelopment of Amsterdam’s Oosterdokseiland island.