The site is located in the center of Hamburg at East area of Hafencity. The program of the competition asked to propose the three residential Twin-Towers on the harbor. Our three Twin-Towers have dual characteristics. First of all, although the 3 Twin-Towers are the same design in order to keep the harmony and to have a clear identity in the environment, their exterior finishes and structures are made of 3 different materials, woods, metal and concrete. Secondly, by having the high performance air-heating system in the walls instead of having it installed in the ceiling, one additional floor can be gained to make it 15 stories. All the apartments can have the double height without compromising the maximum floor areas. Thirdly each double height window facing the terrace is made of glass shutter for wide and easy opening to connect interior and exterior.