East Palo Alto
While Palo Alto is considered one of the more affluent areas of Northern California, East Palo Alto has a less posh reputation. In the early 90s it had one of the highest murder per capita rates in the USA.
East Palo Alto is known locally as one of the more dangerous cities in the Bay Area; it is not a town for random sightseeing. There are many perfectly decent shops and restaurants, but it is best to know where you are going and not to wander aimlessly.