Silicon Valley is geographically based too, and its center of gravity has shifted from Santa Clara County and the Valley proper, where the great first and second generation tech companies started, up through Palo Alto and Menlo Park in San Mateo County, and more recently, towards San Francisco proper.
Prior to the Season 3 finale your appearances were confined to flashbacks (on account of David being dead and all).   Brazil, with a population of almost 200 million is the most populated country in South America.
The city is by far the most dangerous in the country, topping even Rio de Janeiro, which most people know for its favelas, or slums. Brazil may host a large part of the Amazon rainforest, but its most populated areas are not places you want to hang out in.