The structure formerly known as Sears Tower (and still called that name by the Chicago faithful) is just across the Chicago River from Union Station. Completed in 1973, the 110-story structure (willistower.com) was the world's tallest building until the Petronas Towers were built 25 years later in Kuala Lampur, Malaysia. The top of the tower features the Skydeck, a glassed-in observation area where visitors can see all of Chicago's structures and a view of Lake Michigan. On a clear day visitors can see parts of Illinois, Indiana, Wisconsin and Michigan. The tower is about a block and a half to the east of Union Station. Crossing over the river via Jackson Blvd. will get you there.
Built by famed Chicago retailer Marshall Field in the 1920s, this two-block, 25-story structure (merchandisemart.com) was the single largest building to host industry trade shows through the 1940s and 1950s. The mart now plays host to wholesale specialists in the home and furnishings industry. Guided tours of the mart are offered, and the first two floors are host to retail stores, restaurants and a food court. The mart is one mile north of Union Station on Wacker Drive and can be accessed via foot or cab.
For decades, Marshall Field's was the retailer to visit in downtown Chicago. It is now home to a Macy's department store (macys.com), a source of discomfort to many Chicago residents. Regardless of who occupies the building, the former Marshall Field's department store still has many of the same features that made the building an architectural landmark from the old days. Floors are built around an entire central area that goes up nine stories to the top. The Field's building is approximately one mile east of the station, at the corner of State and Washington.
A stretch of Michigan Avenue north of the Chicago River took on a life of its own in the 1970s when Water Tower Place (shopwatertower.com) opened in 1975. Major specialty retailers, including Neiman-Marcus (neimanmarcus.com), Saks Fifth Avenue (saksfifthavenue.com) and Tiffany and Company (tiffany.com), soon followed, and what was a quieter stretch of Michigan Avenue soon became one of the business centers of the city. The stretch of Michigan Avenue begins about 1.5 miles northeast of Union Station, so if you have time access it via cab.
Chicago's blocks-long lakefront Millennium Park (millenniumpark.org) incorporates old and new. Grant Park, the city's long-cherished lakefront green space, was rebuilt and renovated into an area that features over 500 free events each year. Since its opening in July 2004, Millennium Park has played host to blues festivals, ice skating, Taste of Chicago and other yearly activities. Lake Michigan's waterfront and the park itself are a little over a mile to the east of the station. It is accessible via foot if you wish to walk through downtown, or you can grab a cab.