 Cast iron also became the standard support structure in the construction of larger greenhouses.English architect and gardener Joseph Paxton experimented with frameworks of timber, cast-iron and glass in the 1820s and 30s, designing ever larger structures, often prefabricated, culminating in the monumental Crystal Palace exhibition hall built in London in 1851.The success of the concept spawned many imitators, as both exhibition halls and greenhouses, which were almost universally constructed of cast iron (sometimes in combination with wrought-iron) in the 19th century.