A shell structure is a thin, curved structural system designed to transfer loads through compression, tension, and shear stresses across its surface. These structures are lightweight yet strong, allowing large spaces to be covered without many internal supports. Shell structures are commonly made from reinforced concrete, steel, or fabric materials and are widely used for domes, stadium roofs, aircraft hangars, and auditoriums. Famous examples include the Sydney Opera House and thin-shell concrete domes designed by Félix Candela (Wikipedia).