Saturday, September 25, is Museum Day, when more than 1,300 museums across the country offer free admission to all visitors who visit the above link, enter some info, and print out a ticket sent via e-mail. Participating museums are spread all over the country—33 in Illinois, for example, including Chicago’s Adler Planetarium and Museum of Contemporary Art, which usually charge $10 and $12, respectively, for general adult admission. The day of gratis entrance is sponsored by Smithsonian Media, and you can sign up to get your free ticket here.