flanking chapels. To the
west are two towers, built between the years 1641 and 1671, and on the
south a very fine renaissance cloister of two stories, the lower having
been built, it is said, in 1524,[91] and the upper about 1730. A choir
gallery too, with an elaborate Gothic vault below and a fine renaissance
balustrade, crosses the whole west end and extends over the porch
between the two western towers. But if the cathedral in its plan follows
the ordinary type, in design and in construction it is quite unique.
Instead of there being a wooden roof as is usual in churches of this
period, the whole is vaulted, and that too in a very unusual and
original manner. Throughout the piers consist of twelve rounded shafts
set together. Of these the five towards the central aisle are several
feet higher than the other seven from which spring the aisle arches as
well as the ribs of the aisle vault. Consequently the vault of the
central aisle is considerably lower at the sides than it is in the
middle, and in this ingenious way its thrust is counteracted by the
vaults of the side aisles; and at the same time these side vaults are
not highly stilted as they would of necessity have been, had the three
aisles been of exactly the same height. All the ribs are of considerable
projection and well moulded, and of all, except the diagonal ribs, the
lowest moulding is twisted like a rope. This rope-moulding is repeated
on all the ridge ribs, and in each it is tied in a knot half-way along,
a knot which is so much admired that the whole vault is called 'a
abobada dos nos' or vault of the knots.

The capitals are more curious than beautiful; the lower have clumsy,
early-looking foliage and a large and curious abacus. First each capital
has a square abacus of some depth, then comes a large flat circle, one
for each three caps, and at the top a star-shaped moulding of hollow
curves, the points projecting beyond the middle of the square abaci
below. The higher capitals are better. They are carved with more
elaborate foliage and gilt, and the abaci follow more exactly the line
of the caps below and are carved and gilded in the same way. (Fig. 42.)

Perhaps, however, the chief interest of the cathedral is found in the
sacristy, a fine large room opening from the north transept chapel. On
its tiled walls there hang several large and some smaller paintings, of
which the finest is that of St. Peter. Other pictures are found in the
chapter-house,