PYCNOSTYLE, in the ancient architecture, is a building where the columns stand very close to each other, only one diameter and a half of the column being allowed for the intercolumniations. According to Mr Evelyn, the pycnostyle chiefly belonged to the composite order, and was used in the most magnificent buildings; as at present in the peristyle at St Peter's at Rome, which consists of near three hundred columns, and in such as yet remain of the ancients amongst the ruins of Palmyra.