A structure composed of a relatively thin shell of concrete. The shells may take the form of ellipsoids or cylindrical sections, or some combination.

Most of them are buildings, including storage facilities, commercial buildings, and residential homes.

Like an arch, the curved shapes often used for concrete shells are naturally strong structures, allowing wide areas to be spanned without the use of internal supports.

Image source: http://www.structuremag.org/article.aspx?articleid=515