St. Patrick's Day weekend has officially arrived, and residents outdoors for events like the Chicago River dyeing maybe noticed some hazy skies surrounding the Chicago skyline.

The 360 CHICAGO Observation Deck is open daily from 9 a.m. to 11 p.m., but keep in mind that last entry is at 10 p.m.

The city is home to some of the most famous skyscrapers in the world, including the Empire State Building and the One World Trade Center. The skyline is a dazzling mix of old and new, with historic ...