The master’s thesis is based on an open international design competition called: Serlachius Museum Gösta Extension which was held in the winter 2010/2011. The purpose of the competition was to find a design for an annex to the art museum placed in the Joenniemi Manor in Mänttä and to get more exposure for the museum through impressive architecture of the new annex. The annex contains exhibition spaces and collection facilities, conference, presentation and office spaces, and restaurant with auxiliary spaces. The design part of the thesis includes a competition proposal that has been developed further and made more precise. The proposed annex is surrounding the manor in a bold way, but also emphasizes the main facades of the manor. The thesi...