The small Alvord Lake Bridge,made from reinforced concrete and built in 1889,leading from the famous Haight Street into Golden Gate Park,is only 64 feet (20m) wide by 20 feet (6.1m) long,yet is a highly important engineering marvel. This is when steel posts are added to the concrete to reinforce it. This is the very first reinforced concrete structure in the whole United State,a concept that the builder,R. L. Ransome was laughed at for. That is,until 18 April 1906,when all the buildings in the city of this type were the only ones to survived the historic earthquake. He also intentionally designed the inside of the tunnel part to look like a real cave,with 'real' stalactites.
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