Museum of Science, Boston

On the Charles River is the Museum of Science in Boston.  We've been to various science museums around the country where they are solely designed with children in mind.  However, this museum will appeal to people of all ages.  There's numerous exhibits, from optical illusions to dinosaurs to space exploration and many others.  In addition to permanent exhibits, there are always changing temporary ones as well.  While we were there, these focused on Geckos and Bonsai trees.

While the museum is located a bit outside the main tourist area of Boston, it's well worth the walk (or train ride) to visit.  Several hours can be spent in this museum keeping you occupied and happy the whole time.

Great Lakes Science Center

Right on Lake Erie, between Cleveland Browns stadium and the Rock and Roll Hall of Fame is the Great Lakes Science Center.  This is a science center built specifically for children.  There is a portion that is dedicated to NASA so that you can learn about various space sciences.  Beyond that, it's a pretty general science museum including many fun and hands on activities for those under 10 years of age.  For adults traveling alone or with older children though, this would probably be best passed on.