Riddle of the Week

Under the bridges and under the sea
Dost public transportation carry thee
To San Francisco and back again
Through the tunnels of darkness and din

Of clanging tracks and concrete walls
Through deep darkness the echoes call
To merchants, clerks, cooks and bankers
Upon them all a ship almost weighed anchor

How many feet from the tracks
Did this anchor drop?
If you have the answer
At Starbucks you will stop.