According to Wikipedia, Palo Alto to the south is twice as dense as Atherton, and Redwood City to the north is almost twice as dense. And both those cities are

According to Wikipedia, Palo Alto to the south is twice as dense as Atherton, and Redwood City to the north is almost twice as dense. And both those cities are not entirely residential, which Atherton appears to be. Also, neither Palo Alto nor Redwood City are particularly dense by urban standards.