An English Argentine investor, Edward Taylor, opened a pier along the promenade in 1855, and the flood-control walls were extended northwards to Recoleta, and south to San Telmo, in subsequent works completed in 1865.

Some of the most prominent contributors to the district's architecture from the era included Francesco Tamburini, Vittorio Meano, Julio Dormal, Virginio Colombo, Juan Antonio Buschiazzo, Mario Palanti, and Francisco Gianotti.

It's seldom referred to as San Nicolás, but usually as The Center ("City Centre"), and the part east of the 9 de Julio Avenue is called Microcentro ("Micro-centre").

The rapid development of the Argentine economy after 1875 made itself evident in San Nicolás with the reclaiming of riverfront land by businessmen Francisco Seeber and Eduardo Madero, and the shore hitherto popular among washerwomen became the Paseo de Julio (today Leandro Alem Avenue).

The construction of Corrientes and Nueve de Julio Avenues in the 1930s further modernized San Nicolás, which had hitherto been limited in its development by its colonial grid of narrow streets.

Subte line C of the Buenos Aires Metro system and numerous local public bus services serve Retiro, and this area is always teeming with commuters and traffic on weekdays.

Opposite the Retiro train terminal, at the northern end of the CBD, is the leafy Plaza San Martín, surrounded by great palaces and hotels.

The section of the Montserrat ward within the business district includes some of the most important buildings in Argentine Government and history, and was the site of the Buenos Aires Cabildo, the colonial town hall.

This was the location of the Illuminated Block, a Jesuit center of higher learning during the 18th century, and today home to the Colegio Nacional de Buenos Aires.

This is Buenos Aires's oldest neighborhood and even today, very little of the cityscape there is less than a hundred years old (except along Belgrano Avenue), thereby making a nearly seamless transition to the likewise historic San Telmo district to the south.

[9] Puerto Madero occupies a significant portion of the docklands and, as the newest of Buenos Aires's 48 boroughs, features the latest architectural trends in Argentina, as well as many tall apartment buildings and office blocks.

Beginning around 1994, however, local and foreign investment led to a massive revitalization effort, recycling and refurbishing the west side warehouses into upscale offices, lofts, restaurants, private universities and luxurious hotels.

[10] Puerto Madero has been redeveloped with international flair, drawing interest from renown architects such as Santiago Calatrava, Norman Foster, César Pelli and Philippe Starck, among others.

The Puente de la Mujer (Women's Bridge), designed in 2001 by Spanish architect Santiago Calatrava, is the newest link between the east and west docks of Puerto Madero.

Notable non-residential structures include the Repsol-YPF Tower, the Hilton Buenos Aires, the Faena Hotel+Universe (one of a number of refurbished former Molinos Río de la Plata silos), and the Fortabat Art Collection museum building.