Over it is a neat but narrow stone bridge of ten arches, which joins the city at its northern angle to the suburbs. On the city side of the bridge is a square tower, with an archway pierced through it, and with embrasures on the top. This is intended as a "tête de pont;" but it is too small for any effective purpose, and, like the bastions on this face, resembles a military plaything; and this defect is the more striking, as the fortifications, from this angle on the land and sea faces, are remarkably handsome and well proportioned. At the north-western point of the city, which joins the mole, is the citadel of Santiago, a clumsy old-fashioned fortification, separated from the rest of the city by a narrow ditch with a stone bridge, but joined by the curtains of the bastions. It is incapable of any respectable defence, except from a semicircular bastion, which forms the point, and commands the moles and entrance to the river. It is now used as a state prison and magazine. The convicts employed in the public works are also lodged in it. This was the refuge of the unfortunate foreigners who escaped from the massacre on the 9th of October 1820; and to the honour of the commandant (Col. Don A. Parreno), and his lady be it recorded, they found there another home. The length of the city within the walls is 1,300 yards Spanish, from N. W. to S. E.; its width 744, and circumference 4,166. The side towards the river, it has already been remarked, is, from the want of bastions, and from the encumbered state of the approaches to it, in a very defective state. The sea and land faces are exactly the reverse of this, being remarkably clear and strong. The land face has a double ditch, and an esplanade of five or six hundred yards in breadth, which towards the river is marshy and swampy, and utterly unfit for military operations. Towards the sea, and for some miles along the coast, is an epaulement, [125] thrown up when in expectation of an attack from the English in 1804. On this esplanade formerly stood a church, from the tower of which the English under Sir W. Draper fired into the heart of the city: [126] it is now razed. There is also a small battery called Charles the Fourth's, on an elevated spot in the marshy ground; it is about 350 yards from the fortifications and is mostly used as an exercising battery. Another redoubt of stone stands at the southern point of the outer ditch, and flanks the sea shore to a considerable distance to the southward: it also serves to cover the head of the outer ditch, which is not carried round the sea face, apparently for want of room, as its crest would nearly approach high water mark in this part.