Martin Rajniš along with Johnny Eisler and Miroslav Masák designed the famous Máj building (now Tesco) in the centre of Prague. Designed in the high tech style Máj was one of Czechoslovakia’s first department stores and is now a cultural heritage site.

The Máj Department Store became a cultural monument by the decision of the Ministry of Culture as of 2 October 2007. (The building, which is linked to the interwar Functionalism and anticipates the high-tech architecture, represents significant evidence of the 1970's architecture either in European context.) However, it seemed for a long time that the cultural monument status would not be most probably granted. The story has yet remained open because the then building owner, the Tesco Company, lodged an appeal.