Colonnade. A colonnade is a row of columns relatively closely
spaced, usually in a straight line connected by an architrave or
arches. It is a characteristic element of basilica construction.
A colonnade is the same as a portico. Sequences of round columns
alternating with square-sided pillars in a distinct rhythm do
not count as colonnades. If a colonnade forms a connection
between two parallel walls, the columns closest to the walls are
generally treated as engaged columns or pillars, that is,
attached to the respective walls. In the architecture of Egypt,
however, classical arrangement was generally abandoned in the
pharaonic period, and instead imposts were positioned high on
the wall to carry the architrave or arches. In classical
architecture down to the fourth century A.D., only uniform
columns were normally used within a colonnade. A rare exception
is formed by the courtyard porticoes of the Temple of Isis at
Philae, belonging to the second century A.D., which in part
contain different types of column