Northern Railroad, an interurban system running from Chico through Sacramento to Oakland which also used some of the Key System's trackage as well as the Key System's ferry pier, and later ran to the Transbay Terminal until 1941. Other properties From the beginning, the Key System had been conceived as a dual real estate and transportation system. "Borax" Smith and his partner Frank C. Havens first established a company called the "Realty Syndicate" which acquired large tracts of undeveloped land throughout the East Bay. The Realty Syndicate also built two large hotels, each served by a San Francisco-bound train, the Claremont and the Key Route Inn, and a popular amusement park in Oakland called Idora Park. Streetcar lines were also routed to serve all these properties, thereby enhancing their value. In its early years, the Key System was actually a subsidiary of the Realty Syndicate. Berkeley's numerous paths, lanes, walks and steps, were put in place in many of the newly developed neighborhoods, often in the middle of a city block, so that commuters could walk more directly to the new train system. Berkeley's pathways are still maintained by local groups. Legacy Signs of the system still remain: The south wall of the lower level (today's eastbound lanes) of the Yerba Buena Tunnel, connecting the two spans of the Bay Bridge, still contains the as-built "deadman holes", regularly spaced refuge bays into which railway workers could duck whenever a train came along. The eastern end of the San Francisco–Oakland Bay Bridge sits on landfill which was added to the northern edge of the causeway which carried the Key System railbed to the ferry piers. The tunnel that Key System trains used to cross under the Southern Pacific (now Union Pacific and Amtrak) tracks to the mole and later the Bay Bridge still exists. It is visible from the Alexander Zuckerman Bike Path, the ramps of the Macarthur Maze, and at the southwest end of the Target store property in Emeryville, a locale that was once part of the Key System yards and shops. A stretch of road in Albany that was built with a wide median for a planned extension (never constructed) of the "G" Westbrae line is named Key Route Boulevard. The Claremont Hotel, built by a Key System affiliate company, The Realty Syndicate, survives as the Claremont Resort. It was the terminus of the "E" transbay line. The