Representing Otto Wagner's first move away from Art Nouveau and Neoclassicism, the Wiener Postsparkasse (Austrian Postal Savings Bank) is regarded as an important early work of modern architecture. The building occupies an entire city block, next to the Ringstrasse boulevard. The bank's façade obviously alludes to classicism. Wagner's key idea was to celebrate modern materials by developing new forms. The entire façade is covered with square marble plates. These are attached to the main structure by aluminum rivets or bolts, forming a pattern. Inside, the main hall is designed like an atrium, with a large glass skylight allowing natural light to enter the heart of the building at all times.