When talking about natural and geographical characteristics: WOW! You will find:
*mountains all over the west side (Cordillera de los Andes), with arid plain in the North and cold forest in the South. You can meet native people all over this Andes line. Their origin is not the same and it is very interesting to get to know them. Please do not take a picture without asking them. Some native believe that you are taking their spirit by doing that, so please respect it.
Visit: Purmamarca (Jujuy), Tren de las Nubes (Salta), San Antonio de los Cobres (Salta), Aconcagua (Mendoza), San Martin de los Andes (Neuquen), Bariloche (Rio Negro), Perito Moreno (Santa Cruz), Tierra del Fuego.
*meseta patagónica, most of the South of Argentina. You will find a gradient from Andes with some lakes, rivers, forest, to desert and windy plains, to those great South Atlantic cliff beaches.
Visit: Peninsula de Valdez, Puerto Madryn.
*the middle of the country is a little difficult to describe, there are small mountains, rivers, dry climate.
Visit Cordoba and Tucuman provinces.
*In the litoral side (NE) you will find very nice wet forest and the Iguazu Waterfalls. Native from this regions have a different origin too, and there is a great influence from Paraguay. You will also find that there are some german colonies here.
Visit: Palmar de Colon, Minas de San Ignacio, Iguazu waterfall (when there is water).
*Pampa and beaches are extended all other Buenos Aires.
Visit: Buenos Aires city (Palermo lakes, San Telmo, Recoleta). Do NOT forget to visit Delta de Tigre! Mar del Plata, etc.