On top of a small hill within the city limits of Walnut Creek, California in Acalanes Ridge Open Space is the remains of this aviation arrow. Before our current GPS satellite & radar, airplane pilots who did transcontinental airmail routes at night would fly following these large cement arrows built high up on ridges or mountaintops, often accompanied by beacons with a light (though not useful on a day like this). While there were over 1500 of them across the country back in the day, about 100 of them remain today, decaying & forgotten like this one. This one is unique for having a double arrow, being the second arrow on the San Francisco-Salt Lake City route operating during the mid to late 1920s. Pilots would follow the beacons & directions of the arrows using a compass to stay aligned w/ each arrow until they encountered the next one, directing them ultimately to Reno & then Salt Lake City. Most of these sites are now gone, particularly during WWII as a means of making sure any enemy aircraft didn't use these features to scout out American soil.
The Bay Area is renowned for its natural beauty, affluence, diversity, and progressive thinking new age reputation. Lots of ammenities, tours and hotels can be found all around the area.San Francisco is the cultural and financial center of the Bay Area, and has the second highest population density of any major city in North America after New York City. It is also a major tourist destination, and transport and accommodation is plentiful, ranging from luxury hotels to cheap accommodation. San Jose is the largest city in terms of population, land area, and industrial development, and is the center of Silicon Valley, a well-known high technology region. Oakland is a major manufacturing and distribution center, rail terminus/hub, and has the fourth largest container shipping port in the United States.Largely because of San Francisco and Silicon Valley, the Bay Area presently ranks second only to the much larger New York City region in number of Fortune 500 company headquarters (April 2010 Fortune Magazine). source: wikipedia