The greater part of the Italian domes of these periods and of this class, simply cover the crossing or the central tower of a cruciform church, and exhibit no important development.
The most original, perhaps, is the dome of the cathedral at Sienna, which stands upon six piers, forming a hexagon, each side of which is equal in width to the nave and choir ([Fig. 438]). In the next stage, the angles are corbelled-out, so as to form in the upper storey a dodecagon, which form is followed out in the dome.
Fig. 437.—Section, Baptistery at Parma.
Fig. 436.—Plan of Baptistery at Parma.
The merit of this plan is that it unites itself, with little obstructiveness, with the church on all sides of it, and opens out in its centre a space of double the width of the nave. It is also pleasing and elegant in its effect. But it is time that we returned to the Byzantine type, which you will remember that we left at Ravenna to follow out this digression.
We now adjourn from Ravenna to Venice.