"I think it was really cool. It was almost like fireworks," said fan Evan Boesman.
However, fans of the sequel weren't the only ones glad to see movie magic in the making. With hotels and restaurants full with the curious, the production could generate revenue of at least $20 million for Michigan Avenue retailers and the city.
"It's very important to know that you can shop anywhere on the Magnificent Mile. The sidewalk accesses are open. So, people can go to Northridge or the Nordstrom anniversary sale. They can go to the art galleries. Everything is open for people to shop," said John Chikow of Greater North Michigan Avenue Association.
Until Monday morning, the Magnificent Mile is closed to vehicle traffic from Randolph to Ontario. Lower Michigan Avenue will be closed between Hubbard and Wacker until 5 a.m. Monday. Filming will also affect some downtown bus routes, as well. In addition to Michigan Avenue, parts of Hubbard, Kinzie, Dearborn, State and Wabash will be closed for several hours over the weekend.
Saturday's heat and humidity didn't deter large crowds of spectators or two dozen actual Illinois National Guard reservists cast as extras.
"I am really excited. It is a great opportunity for anyone in the Illinois National Guard. It is a phenomenal opportunity," said Sgt. Michael Pett.
Although some scenes for Transformers 3 were shot in Los Angeles, the majority of the movie is being filmed in Chicago. But unlike fictional Gotham City in the Batman film, 'The Dark Knight,' also shot in Chicago, this time the city is being showcased.
"Chicago was the backdrop, and this has generated so much excitement and so much fun," said Rich Moskal of the Chicago Film Office.
As part of Saturday's filming, cars were strewn about the Michigan Avenue bridge, which was in the up position. ABC7 is told crews could possibly shoot some scenes on the Chicago River Saturday night.
After production is completed on Michigan Avenue, crews will then move to the area between Michigan and Wabash.
Chicago residents should expect film crews to be in town until late August.