Editing Keystone (architecture) (section)

==Architecture==
In a [[Rib vault|rib-vaulted]] ceiling, keystones commonly mark the intersections of any two or more arched ribs.  For aesthetics, keystones are often larger than ribs in vaults and many of the [[voussoir]]s (arch stones) in arches, or embellished with a [[boss (architecture)|boss]]. 

A "dropped keystone" is one where the keystone projects lower than the other voussoirs. Following [[Giulio Romano (painter)|Giulio Romano]], [[Mannerism|Mannerist]] architects of the 16th century often designed arches with enlarged and slightly dropped keystones, as in the "church house" entrance portal at [[Colditz Castle]]. Numerous examples are found in the work of [[Sebastiano Serlio]], a 16th-century Italian Mannerist architect.