pentagons also occur in nature: fruits of the okra are pentangular. the flowers of ipomoea are pentagular. in chemistry, many cyclic compounds are pentangles: cyclopentane and furan are examples for this. in architecture, many bastions are pentangular: bourtange, in the netherlands has been completely restored, and is a pentangle. the citadel of lille, nyenschantz, near st. petersburg, or the citadel of pamplona are . the villa farnese is a palace in the form of a pentagon, so is the castle of nowy wiśnicz. the pilgrimage church of saint john of nepomuk near žďár nad sázavou also uses a pentangular design.