Estancia La Cinacina in San Antonio de Areco (about 112 km from the city of Buenos Aires).
www.lacinacina.com.ar. (Information both in English and German on their web site!)
I visited in March this year and I have seldom seen such an awesome and impressive show like this one above that I filmed. I'm sorry for the quality, it was blowing and I was trying to take pictures with one hand and filming with the other....
I really recommend Argentina for a visit and obviously that should include their culture - wine, meat, bola dancing and horse shows...!