Have you ever walked by a building and thought, I wish I could see what’s inside?

Now you can. The Chicago Architecture Foundation presents the fourth-annual Open House Chicago, a free public festival that offers behind-the-scenes access to 150 buildings across Chicago. No tickets are required and everyone is welcome.

On October 18-19, you can explore Chicago’s hidden gems from Rogers Park to Pullman and everything in between. Tour Frank Lloyd Wright masterpieces, repurposed mansions, stunning skyscrapers, vacant theaters, exclusive private clubs and more.

Follow along on social media with @chiarchitecture and #OHC2014.

More info at www.openhousechicago.org.