Havana is a place of considerable strength, and, besides the walls and ditches which surround it, the city is defended by six strongholds, called the Moro, the Cobanas, No. 4, the Atares, the Principie and the Putna. The first and last serve to protect the entrance of the harbor, the second is a sort of citadel and the others are so placed as to cover the approaches by land. The line of fortification, embraces a sort of irregular polygon of an eliptical form, the greatest diameter of which is 2,100 yards, and the smallest 1,200 yards in extent. The entrance between the Moro and Putna, castles is about 1,500 yards long, and in its narrowest part 350 yards wide. In the arsenal of the Havana, there have been built 49 ships of the line, 22 frigates, 7 packet ships, 9 brigs of war, and 15 schooners of war. The town is built on the western side of the basin, near the channel, on a kind of promontory. The suburbs, or _barrios esta muros_, cover more ground and contain a larger population than the city itself, and yet they are so intimately connected with it, that the first of the houses in the suburban street, stands on the very edge of the _glacis_. The streets are narrow, crooked, and generally unpaved, but they contain some well-built houses. There are, too, several good buildings among the churches, one of which contains the remains of Christopher Columbus. The other large edifices, as the Palace of the Government (shown to the right of the engraving,) that of the commandant of the marine, the arsenal, the post-office, and the building used for the manufacture of tobacco, are less remarkable for their architecture than for their solidity. Besides these, the city contains nine parish churches; six other churches, connected with hospitals and military orders; five chapels or hermitages; the Caza Cuna, a foundling hospital; and eleven convents, four for women, and seven for men. The other public establishments are the University, the colleges of San Carlos and San Francisco de Soles, the Botanic Garden, the Anatomical Museum and lecture rooms, the Academy of Painting and Design, a school of Navigation, and seventy-eight common schools for both sexes. These places of education are all under the protection of the Patriotic Society and the municipal authorities. The charitable institutions consist of the _Caza de Beneficiencia_, for both sexes, a penitentiary, a Magdalen Asylum, and seven hospitals--one of them contains a lunatic asylum. There are, besides, three theatres, an amphitheatre for bull fights, _plaza de toros_, and several public promenades, such as the Alameda and the Paseo Nuevo; In Turnbull's "Travels in Cuba," published by Longman & Co., London, 1840, the city is said to contain 3,671 houses within the walls, all built of stone; and in the suburbs, 7,968, of various materials. The number of private carriages for hire amounted, in 1827, to 2,651, and they are certainly now more numerous.