Look, we know how summer goes. Come August, you realize that you've been on a three-month bender and didn't partake in any of the cultural stuff you swore you'd try. (No, the Rib America Festival does not count.) So knock out everything on one day and make it a Friday: That's when you'll take in the city's cultural landmarks for almost zero cash. Park for free in Dogtown, cross on foot at the Tamm Avenue bridge and start your day with the critters at the Saint Louis Zoo. Get there before 9 a.m. and you can enjoy some exhibits — such as the stingrays at Caribbean Cove — without admission price. Next, catch the Forest Park Trolley (tickets are $1 for kids, $2 for adults and valid all day). Ride it down to the Saint Louis Science Center and see if you've gotten any better at building that vexing foam arch from the last time you were here. Don't think about it for too long, though, because it's time to board the trolley again and beeline it to the Missouri History Museum where you can enjoy a light lunch at Bixby's. Next up, the Saint Louis Art Museum: Because it's Friday, the museum's featured exhibitions are free of charge. Zip to the Boathouse in Forest Park for an alfresco dinner and a drink, and board that trusty trolley once more (before the service ends at 7 p.m.) for a free performance of Othello by St. Louis Shakespeare outside the art museum, or settle into one of the Muny's free seats. A crash course in zoology, science, history, art, English literature and drama with nary a buck paid for admission? Consider yourself summer schooled, all in one glorious Friday.