Considered one of the most beautiful examples of the art nouveau style, this hotel created quite a sensation when it opened back in 1906. Located on the Danube, the Gresham Palace reopened as a Four Seasons Hotel in 2004, following a 30-month restoration. An army of skilled craftsmen devoted their efforts to restoring the fantastic art nouveau elements, the curving stairways, the conservatory, and the valuable lead glass windows with their floral motifs.