Chicago has always been an innovative city when it comes to architectural design and reaching for new heights. The Sears tower (now called the Willis Tower) held the world's tallest building title for nearly 25 years. Well before that, though, a building not known for its height, but for its area was the king of the world.

The Merchandise Mart in downtown Chicago was built in 1930. It is so big it had its own zip code all the way until 2008.

This mega building is home to manufacturers' showrooms, offices, restaurants, art installations, and much more. It is still a leading retailing and wholesale location with over 20,000 visitors a day.

This beautiful art deco building is an icon of the Chicago area displaying colorful celebrations of light at night that change based on holidays or special events.

The building is so big it has its own train station. This amazing feat of engineering was built in under four months in 1930.

The main line of Chicago Transit Authority's North Side Division runs through this station. It is one of only two commercial buildings to have its own station.

Chicago's Riverwalk passes in front of the Merchandise Mart where you will find the Merchandise Mart Hall of Fame showing bust sculptures of eight legendary American merchants.

The Merchandise Mart was built by Marshall Field & Co. and later owned by the Kennedy family for over 50 years.

Marshall Field was an innovator and retail magnate dominating the upscale department store industry for decades. He along with notable founders of Sears Roebuck, Montgomery Ward, and Woolworth are among the eight busts outside the main entrance to Merchandise Mart.

Think of the Merchandise Mart as the ultimate shopping destination for retailers, with hundreds if not thousands of full showrooms showing off the latest in design.

Around 50 percent of the building is used for these wholesale showrooms. Imagine fully furnished and staged rooms where you can find inspiration for your home renovations. Since 2010, these showrooms have been open to the general public.

In fact, it is said that the Sultan of Brunei furnished his entire palace after a week-long visit to the Merchandise Mart. He dropped $1.6 million on his little shopping trip.

The Merchandise Mart has always been a retail innovator, but that isn't its only claim to fame. It has always been involved in culture and the arts as well.

You can find regular art installations in the main lobby and throughout the building from sculpture to murals, and even entire digital art displays on its 2.5-acre "canvas" - the front of the building that faces the Chicago River.

Have you ever stepped foot in this amazing center of retail extravagance? Tell us all about it with a comment. Chicago is filled with amazing buildings and attractions. Here are a few more downtown Chicago destinations you should check out.