The simplest type of central building is a circular edifice.

Pl. LXXXIV, No. 9. Plan of a circular building surrounded by a
colonnade.

Pl. LXXXIV, No. 8. Elevation of the former, with a conical roof.

Pl. XC. No. 5. A dodecagon, as most nearly approaching the circle.

Pl. LXXXVI, No. 1, 2, 3. Four round chapels are added at the
extremities of the two principal axes;--compare this plan with fig.
1 on p. 44 and fig. 3 on p. 47 (W. P. 5b) where the outer wall is
octagonal.

Group II.

Domes rising from a square base.

The plan is a square surrounded by a colonnade, and the dome seems
to be octagonal.

Pl. LXXXIV. The square plan below the circular building No. 8, and
its elevation to the left, above the plan: here the ground-plan is
square, the upper storey octagonal. A further development of this
type is shown in two sketches C. A. 3a (not reproduced here), and in

Pl. LXXXVI, No. 5 (which possibly belongs to No. 7 on Pl. LXXXIV).

Pl, LXXXV, No. 4, and p. 45, Fig. 3, a Greek cross, repeated p. 45,
Fig. 3, is another development of the square central plan.