http://www.teatrocolon.org.ar/
A quick & easy 2 day trip from BA is Iguazu Falls. Iguazu Falls is one of the 7 Natural Wonders of the World. It is mind bogglingly beautiful. Words cannot adequately describe. If you want to explore more of Argentina than the city of BA (and the surrounding towns where the wedding will be), this is a GREAT option. Stay at the Gran Meliá Iguazú, which is the only hotel located within the national park itself. https://www.melia.com/en/hotels/argentina/iguazu-national-park/gran-melia-iguazu/index.htm?utm_source=listing&utm_medium=organic
Take the ferry across the widest river in the world for a nice day trip from B.A.