On the roof large, circular “light eyes” will serve as skylights down into the station below and operable windows in conjunction with ventilation tubes will eliminate the need for mechanical ventilation. The use of natural daylighting and ventilation minimizes energy needs for the station and additional lighting will be energy efficient and be provided for via a photovoltaic system on the existing northern station building. Concrete is used to construct the underground station and is painted in light colors in order to reflect natural light during the day.
Just to reiterate, this whole project was designed in 1997, long before some of us were even thinking about sustainable architecture, so the concept of light wells and ventilation tubes was really quite innovative. Main Station Stuttgart is part of a large rail redevelopment project, called Stuttgart 21, which includes restructuring the rail node in Stuttgart and constructing a high speed rail line Wendlingen and Ulm and linking it with other major European HSR nodes. This project also received a Gold Global Holcim Award in 2006.