In Structures, students explore materials and designs of towers, bridges and other structures. A good overall resource for the unit is the Exploritorium's Structures Around the World
In one activity in this unit, students build towers from 3" x 5" file cards. Can students top one made by teachers?
An excellent interactive site for bridges is Nova Online's Super Bridge. Check it out. You might want to visit two of New York State's most famous bridges, the Peace Bridge and the Brooklyn Bridge. The Association of Bridge Construction and Design has a lot of interesting links. A good student book on the subject is Bridges by Ken Robbins.
For information on skyscrapers, visit Skyscrapers: Twentieth Century. Two other good sources are The Skyscraper Page and the Skyscraper Museum. The PBS series "Building Big" has Web resources on how bridges, skyscrapers, domes, dams and other large structures work.
Architecture in America has pictures of a variety of buildings as does Architecture.com, a British site. Also of interest are the PBS pages on Frank Lloyd Wright, perhaps America's most famous architect. Building structures requires engineering skills and The Sightseer's Guide to Engineering gives some places to go to learn about engineering and to see its results.
For information about concrete, visit Concrete Basics developed by the Portland Cement Association.
For information on how houses are built, see How House Construction Works.
The Franklin Institute has exhibits related to structures and a page with useful links.
The Lemelson Center's Invention at Play has online activities that relate well to the creative inventing and building that this unit involves.
Below are some pictures of structures built by Ms. Vigdor's third grade class in Penfield, NY, using this unit.