Developed by urban landscape developer Mori Building, the Toranomon Hills area was built around a new loop road and "opened" in its current form in 2014. Mori has now announced its intention to develop the complex further into a Global Business Hub, covering an area of about 7.5 ha (18.5 ac).
The existing mixed-use tower on the site has 52 floors spread across a height of 247 m (810 ft). It houses office space, conference facilities, luxury residences, shops and restaurants, as well as 6,000 sq m (65,000 sq ft) of green space.
A new 36-floor tower designed by German architect Christoph Ingenhoven will provide 94,000 sq m (1,012,000 sq ft) of new office space and an innovation center. In addition, the Toranomon Hills Business Tower will house two new bus stations, connecting the area to central Tokyo and the bay area and to nearby airports.
The planned 56-floor Toranomon Hills Residential Tower will add around 600 residential units to the 200 already in the area. Residents will be housed in large units and serviced apartments with "Western-style en-suite bathrooms." They will also be able to make use of an on-site spa and fitness center, childcare facilities and a 24-hour bilingual concierge.
Finally, the Toranomon Hills Station Tower will provide a mix of office, hotel and retail space and will incorporate a new subway station. The tower will be designed by OMA, the firm's first in Tokyo, and will have a striking geometrically offset aesthetic.
The planned new development will see the complex grow into a self-contained area with links to the rest of the city and 15,000 sq m (161,000 sq ft) of elevated green space. This elevated park will contribute to the area's independence, allowing people to get around the complex, but also provide links to the adjacent Mt. Atago slope and the Atago Green Hills complex.
Mori Building says the green space will be "a refreshing and an eco-friendly nature island," with a variety of trees and plants. Not only will it provide a means for people to move around the area and beyond, but it will act as a space for leisure and relaxation, too.
The Toranomon Hills Business and Residential Towers are due for completion by 2019, while the Toranomon Hills Station Tower expected to be completed by 2022. Some subway services are expected to be running in time for the 2020 Olympics in Tokyo.