Nathan Masters has a great post at KCET on the history of the tunnels that used to carry traffic in and out of downtown Los Angeles. Hard to see today, but Downtown was encircled on at least two sides by big hills that blocked access. As L.A.'s outlying areas grew, the traffic poobahs punched through the hills with tunnels. The photo above shows the Hill Street passages looking north from 1st and Hill — the tube on the left was for transit streetcars, the tunnel on the right for drivers. There was another tunnel a block away on Broadway that came out about at Temple Street. Gradually, the hills were bulldozed away almost entirely. The arts high school on Grand Avenue sits on about all that is left of Fort Moore Hill, a prominent feature in early photographs of the city.
Masters aggregated some fun photos from various sources. Below: A 1958 air raid drill in the Pacific Electric subway tunnel that ran under Bunker Hill.
Top photo California Historical Society Collection, USC; Bottom, Los Angeles Public Library.