The City of La Plata was designed as a new city in 1882, to serve as the capital of Buenos Aires Province after Buenos Aires itself had become the national capital. So it's a city that was designed at a drawing board according to a rigorous plan. I visited it on a day trip from Buenos Aires. It's a ride of about one hour, and buses leave every 5 or 10 minutes. My planning wasn't too great, as it turned out to be Columbus Day (a national holiday). When I walked from the bus station to the central area, the only creatures I came across were dogs and the city's lowlife.
Finding your way is easy in this planned city: the streets have no names, only numbers. There's a large city map at the bus station, where you can see that the city is a perfect square with 40 horizontal and vertical blocks. They are crossed by some diagonals, for the creative touch. The planners were environmentally conscious avant-la-lettre and had envisaged 'urban forestry', parks and gardens. I visited one of those, the Paseo del Bosque. There's a zoo and the large Natural History Museum where I met my Glyptodon friends again (see Colonia de Sacramento review).
With the city's Casa Curutchet, one of Le Corbusier's buildings, right on track to become a WHS in 2009, the remaining chances for the city as a whole are slim. Also, I don't think any (relatively) modern planned city can surpass the extremities of Brasilia. So, if you're in Buenos Aires and got half a day to spare, do visit La Plata but don't expect to be blown away by it.