Keystone Office, Praga, Czech republic New modern architecture of Karlin district, Prague. After the devastating flood in 2002, several administrative buildings were built in this part of Prague. The “Keystone office” building is one of them. Architectonically unique Object “Keystone”, which is a modern interpretation of Czech Cubism. The project bears the unmistakable manuscript of Swiss architects Mathias Müller and Daniela Niggli from the world renowned Swiss architectural office EM2N.