The concept of a green skyscraper is by no means new, but Vincent Callebaut's DNA-inspired design is impressive nonetheless. Construction recently started in Tapei on Agora Garden, which has two sections that twist a full 90 degrees as they ascend. The resulting twenty-story building will resemble a giant double helix on completion, permeated by hanging gardens on every floor and surrounded by a small forest. The building will be topped off with an array of solar panels, while the hanging gardens will be fitted with composting facilities, bird nests, and rain water tanks that irrigate the plants. It's hoped that the wide range of plants will encourage wildlife and improve air quality for residents.

Callebaut hasn't provided any energy efficiency estimates — we don't know how much power will be created by the building's solar panels, nor do we know how large the planting effort will be in its hanging gardens or ground-level forest. Without facts and figures, It's difficult to take its green credentials seriously right now — other buildings, such as Boeri Studio's stunning Bosco Verticale, have been designed from the ground-up to improve the air quality of entire cities. Agora Garden should be completed by 2016, when it'll play host to around 40 apartments. One of the benefits of the double-helix design is it'll look different from almost every angle — you can see a full range of views over at Vincent Callebaut Architecte's site.