If you visit between December and March, you can ice skate on Frog Pond, the ice skating rink in the Boston Common, America’s oldest public park. The 50-acre area was set aside in 1634 as a military “training” ground and common pastureland, but it has always been a place where city dwellers convene for anything from a political rally to sunbathing. Adjacent to the Public Garden and across from the State House, these two beautiful green spaces are an oasis in the heart of the city.