CHICAGO - A Chicago landmark is marking a big birthday.
The Willis Tower is celebrating 50 years along the city's skyline.
A celebration was held on Thursday, with an open house commemorating the role that building, formerly known as the Sears Tower, has played in Chicago history.
The celebration featured live music, art exhibits, photo ops, and some giveaways.
The Chicago Gay Men's Choir is among the performers featured, and some Chicago sports mascots were also on hand.
The 110-story tower is also showing off a recent $500-million renovation that includes new dining and community space.
Additionally, the open house served as a kickoff for the Willis Tower Outdoor Summer Concert Series. Concerts will be held every other week on Thursdays, on the fourth-floor terrace.