id you know that Chicago has a massive building with its own zip code? That’s right, and in 1930, the Merchandise mart opened its doors to the world as the largest building in the world. The 4 million square foot area served such a large influx of visitors daily that it required its own L stop and connection to Chicago’s now abandoned 60 miles of underground freight tunnel. Perhaps what mystifies me most is that Merchandise Mart was built above a massive train yard and that, for many decades, sub-terrain freight train delivery was possible in the heart of Chicago. This near-century-old art deco masterpiece still stands on the bank of the Chicago river and serves around 20,000 people daily in modern times.