Although there are not many cities in the world as architecturally homogeneous as Brasilia, there are certainly fewer that resemble Buenos Aires, whose most obvious characteristic is its variety.
The façades of the city seem to be illustrations out of a book on Argentine history, but with pages in disorder. In front of the Italian style Government House there is a Colonial Cabildo, an unfinished neo-classical Cathedral, the monumental Banco de la Nación and the Ministry of Defense, and the fronts of several public buildings that may remind you of Italian or Soviet architecture of the '30's.
If you keep on walking, you'll find Corbusian rationalism and Bauhaus, or steel and glass boxes in Mies Van der Rohe style. There are Colonial churches dripping 19th century mouldings, a Ministry of Education in German Renaissance style, or neo-gothic constructions in good local-made brick with cement veins. Neo-colonial and neo-hispanic buildings in concrete rub shoulders with old markets in iron and glass, and railway stations and harbour buildings are identical to those in England. Parks and squares planned according to French Romanticism are lined with Tudor houses and Mediterranean "sausage houses", while in many small and large mansions, Gaulish academism or Louis XV style are more or less distorted by distance from the originals and the different materials employed: none of them are made of stone. There is no lack of indeterminate styles - Argentinian expressionism? - like the lovely Barolo (1366, Mayo Avenue) and the incredible palace-pool of the Water Works (1950, Córdoba Ave.).
Looking upwards, Buenos Aires displays its love of ornate moulding, mortar caryatids, 'Parisian' cupolas and some art-nouveau. There is some spontaneous architecture in La Boca and the poorer suburbs; meanwhile, local post-modernism plays around with the fronts of pizza shops, supermarkets and shopping centers.

Buenos Aires does not lend itself, like other great capitals of the world, to rigid and schematic tours, therefore three basic itineraries are suggested:

I - From Plaza de Mayo to San Telmo

Along 15 km approximately, walking along Defensa St., with some detours, is probably best to see what remains of the old city and some suggestive corners of Buenos Aires.
Plaza de Mayo may seem a little austere to be the political centre of what was one of the most prosperous nations in the world. The lack of stone, the peripherical position of the Viceroyalty of the Río de la Plata in relation to the metropolis, and the changing taste and fashion in architecture, contributed to the actual conformation of this space.
The Cabildo was the headquarters of the City Council. Its final construction was done in 1725. The actual building - result of reiterated modifications - is the seat of the Museum of the May Revolution and of the Cabildo. The Government House (Casa Rosada) is built on the site where the city Fortress stood till the middle of the 19th century.
The Banco de la Nación was designed by Alejandro Bustillo, and built in 1939.
Avenida de Mayo (towards Congress) is the only architecturally coherent street in the city, since only fifteen years went by between its inauguration -in 1894- and the completion of most of its buildings (newspaper La Prensa, restaurant Pedemonte, the Café Tortoni, the Hotel Castelar, the Barolo Palace, the Congress - one of the most imposing and better built edifices of the city).
From Plaza de Mayo to the left, we'll get to the dispersed 'historic centre' of Buenos Aires. The Manzana de las Luces has the Church of San Ignacio and the Colegio Nacional de Buenos Aires. We'll then see the Basilica of San Francisco, the Museo de la Ciudad - this 19th century house was one of the first 'two-storey buildings' in Buenos Aires. We'll then arrive at the Basilica of Our Lady of the Rosary. Very close to Plaza Dorrego you will find the Museo Penitenciario (Penitentiary Museum), one of the oldest buildings in the city. To one side of the Museum is the beautiful Church of Our Lady of Bethlehem. Pasaje Defensa has a two-storey sausage house. The casa chorizo is, if it really exists, the typical dwelling of Buenos Aires. This type of house follows the tradition - through Andalusian buildings - of the ancient Roman houses of 2,000 years ago. They are composed of a series of rooms looking onto an inside courtyard. The name sausage house is due to the length of the porteño plot, 8m wide by 40m in length.

II - The river

The neighbourhood of La Boca lies to the south. During the second half of the 19th century, a large colony of Genoese immigrants settled in the area. With some ingenuity and sacrifice they managed to overcome lack of means and materials with practical architectural solutions which disguised poverty with picturesque housing.
In this sector the Costanera Sur runs from the Ciudad Deportiva de la Boca along the river.
One of Lola Mora's most famous works is found here, the Fountain of the Nereids. The old warehouses of Puerto Madero have been transformed, in the early '90's, into cultural centres, restaurants, shops and lofts, bringing new airs to the river. On the other side of Dársena Norte starts the Puerto Nuevo. Between it and the city there are several institutional buildings and Retiro Train Station, near Plaza San Martín. Several important buildings contribute to making Plaza San Martín an interesting corner of the city. The Círculo Militar is an outstanding example of French Academism. The Palacio San Martín, headquarters of the Foreign Office, is on the other side of the square. The Plaza Hotel is one of the most traditional in the city. Next to the Plaza stands the towering Edificio Kavanagh, built in 1935. For many years the Kavanagh building was the tallest concrete construction in the world. On the other side of the avenue are the enormous iron galleries of Retiro Train Station, brought over piece by piece from England: this is an attractive example of railroad architecture. The Sheraton Hotel and the Catalinas Norte complex are on the other side of the square.

III - The woods and streets of Palermo

Opposite the Monumento de los Españoles, one of the most handsome in the city, is one of the gates to the Zoo. The Zoo, opened in 1889, is one of the last examples of 19th century 'zoological architecture' left in the world. Nearby is the Sociedad Rural and the Botanical Gardens, which opened in 1898, and are designed by the architect Carlos Thays.
El Rosedal Park, also designed by Carlos Thays, is the culmination of the many works of French Romantic inspiration built in several cities of the country between the end of last century and the beginning of the present. During this time, the colonial 'dry squares' disappeared, replaced by the actual 'green square'.
In Palermo Chico the square layout of the streets of Buenos Aires disappears and the streets wind and cross like in any European city. The place keeps the character of the rich families that once occupied it, but today most of its buildings belong to embassies.

The Colón Theatre, on Avenida 9 de Julio, can not be left behind from this architectural tour. It is one of the most important lyric theatres in the world. It was projected by Tamburini and built by Víctor Meano and Julio Dormal, and is an Italian style building with French decoration. The main auditorium can hold 3,500 spectators and the cupola was painted by the plastic artist Raúl Soldi.
In Recoleta district some of the most interesting examples of French influence in porteño architecture follow each other along Alvear Ave. The Recoleta Cemetery was inaugurated in 1822 and remodelled in 1886. The entrance has a neo-Doric façade and such masters as Tantardini, Fioravanti or Riganelli have signed the numerous tomb sculptures.