The Retiro, occupied as barracks, is on the north extremity of the city, and has nothing worthy of notice about it, but its theatrical appearance, and daubs of paintings on the walls. There is a large space in front, called the Bull Ring, in which bull-fights used to take place. The band performs there, for a short time, in the afternoon. It is here that criminals are shot, when the punishment is not for a state offence. Being situated upon high ground, and near the river, the Retiro has a pleasant prospect. In one of the streets near it, is a large brick building, built for a distillery, twelve years since, by Mr. Thwaites, an Englishman. The speculation did not answer, and the house is now in a state of dilapidation. A windmill, west of the town, is a conspicuous object; it is the only one in the country, and was erected by Mr. Stroud, also an Englishman. It had, for some time, the fate of the distillery; but I have heard that it now flourishes. The Residencia, on the south side of the Fort, is appropriated as an hospital. There are two or three other public hospitals, including one for foundlings. * * * * * The Grand Plaza is a large square, environed by buildings: on the east is the Recoba, a piazza with shops; on the west, the Cabildo; on the north, a part of the cathedral; and on the south, a range of shops. There is a pyramid in the centre, which, on festival nights, is illuminated. If paved, it would be an admirable place for the parade of troops; at present, wet weather renders it almost impassable. A second Plaza has been made, adjoining the other, near the Fort, by the removal of the market-place and some dirty sheds and stabling. The river, the fort, some neat buildings on the south, the handsome arch, under which there is a passage to the two plazas, the towers of St. Francisco's church, and the Cabildo, taken in perspective from Faunch's Hotel, would form a good picture. At night, the streets are respectably lighted by lamps fastened to the walls, which extend as far as the eye can reach in some of the principal thoroughfares, in St. Francisco Street particularly. A stranger, on viewing this street, would imbibe no mean opinion of the city. The lamps do not afford any thing like the illumination of the gas lights of London; they are equal, however, to those used before the introduction of gas. From the state of the pavements, except in the principal streets, walking at night is very disagreeable--in wet weather, dangerous; and here are no accommodating hackney coaches to jump into. It is intended to pave all the streets; but, from the scarcity of workmen and materials, it will be some time before this can be effected. Those that have pavements, bating their narrowness, are similar to the streets of London; the unpaved ones are very miserable. * * * * *