Join Brian Brenner for a guided bike tour around the Esplanade and Charles River bike paths.  Learn the inside story of the history of the Charles River basin bridges.  Hear about design of the Zakim Bridge.  Learn about Smoots.  Get an update on the repair of the Longfellow Bridge.  The tour will be scheduled for a late spring/ early summer Sunday afternoon.  It involves about 10 miles of biking on flat trails, about 2 plus hours.  Participants should be in good shape and will either transfer their bikes to the departure point (on Memorial Drive in Cambridge) or will make arrangements with the tour guide.  The tour is not appropriate for younger children.  The trip finishes with some refreshing Kedem sparkling grape juice and snacks by the Charles River.