 Some, like the tower at Santa Croce, have large openings of Gothic form and are surmounted by spires.In addition to towers and spires, great mediaeval churches may have several other architectural forms rising above the roof-line, particularly over the crossing.These include the octagonal tower at Burgos Cathedral, the wooden octagonal tower at Ely Cathedral and the octagonal dome of Florence Cathedral, conceived in the late Gothic period and engineered by the Renaissance architect Filippo Brunelleschi.