Originally inhabited by the Ohlone Indians, explored by the Spanish, colonized by Mexico, and the U.S., Oakland has maintained its rich cultural heritage. Oakland's charm exceeds its man-made wonders. The tumbling hills, vast forests, and other natural wonders provide for outdoor escapes amid the urban environment. According to a University of Wisconsin study, Oakland is the most ethnically diverse city in the U.S. Oakland events include: Cinco de Mayo, Festival of Greece, Chinatown Streetfest, Black Cowboys Parade and Heritage Festival, and Silver Star Pow Wow and Indian Market.