Pack a swimsuit and towel and rent a bike on the Greenway from Urban AdvenTours for $35 and pedal five minutes to North Station. Board the Fitchburg Line (bikes are allowed on weekends) for the 40-minute trip west to the Lincoln station. Cycle 2.3 miles to the 1938 Gropius House, home to Bauhaus founder Walter Gropius. Less than a mile away is the 35-acre DeCordova Museum & Sculpture Park, New England’s only ongoing exhibition of contemporary outdoor sculpture. The museum’s café has picnic kits that include food, a basket, and a blanket to unfurl next to your favorite piece of art. If you’re there between June 5 and September 7, go into the museum to see “The Old, Weird America: Folk Themes in Contemporary Art” with works by eighteen artists including Kara Walker and Matthew Day Jackson. Head back to Boston via the Concord Road and stop off for some transcendentalism and a swim at Walden Pond. Ride Concord Road for another two miles and take the Boston-bound train from Concord Station.