Maman is probably one of the most famous sculptures of today. It is a gigantic spider in bronze which carries marble eggs, made by Louise Bourgeois (1911-2010). This is without any doubt her most famous work. You can see this spider permanently in a couple locations. In London, Kansas City, Otawa, St Petersburg, Tokyo, Bilbao, Seoul and Des Moines. And she has visited Paris, Boston, Washington, Oostende (Belgium)and is now in BA.
Fundacion PROA is a very nice museum in La Boca, and has a really nice restaurant with a view over the river, and a beautiful library. Certainly a must-do!