f which the name of one portion (the keep) has gradually come
into use as a synonym for the whole. Of the various fortress-palaces of
Europe, not one can lay claim to so long or so interesting a history.
The Louvre at Paris, though still in existence, is so as a comparatively
modern palace, in which nothing now remains above ground of the castle
of Philip Augustus, with its huge circular keep, erected by that monarch
in 1204. The Alhambra at Granada is of a by no means so remote
antiquity, as the earlier portion of it only dates from 1248, while the
Kremlin at Moscow only goes back to 1367. Probably the sole building
erected by a reigning monarch as a combined fortress and palace at all
comparable with the Tower of London is the great citadel of Cairo, built
in 1183 by Saladin, which, like it, is still in use as a military
castle; but, secure in its venerable antiquity, the Tower is superior to
all. The greater portion of the site upon which the Tower stands has
been occupied more or less since A.D. 369, when, according to Ammianus,
the Roman wall surrounding the city of London was built. At this point,
which may be termed its south-eastern extremity, the wall crossed the
gentle slope that descended to the Thames bank, on reaching which it
turned westwards, the angle being probably capped by a solid buttress
tower or bastion. Although Roman remains have been found at various
points within the Tower area, it is not likely that any extensive
fortification ever occupied the sloping site within the wall at this
point, for the original Roman citadel must be sought for elsewhere, most
probably upon the elevated plateau between the valley of the Wallbrook,
and Billingsgate, where even now there stands in Cannon Street, built
into a recess in the wall of St. Swithin's church, a fragment of the
ancient Roman milestone, or _milliarium_ (known as "London Stone"), from
which all distances along the various Roman roads of Britain are
believed to have been reckoned. From what is known of the Roman system
of fortification, it is obviously improbable that there should have been
any extensive fortress erected upon the site where the Tower now stands.
Not only would this have been opposed to the Roman practice of placing
the _arx_, or citadel, as far as possible in a central and dominating
position, but in the present instance it would actually have been
commanded by higher ground to the north and west, while to the east free
exit to the o