It was only a two lane road.

那是一条双车道公路。

Seven hundred and twenty-six feet tall and six hundred and sixty feet thick at the base, Hoover Dam contains enough concrete to pave a two lane road from San Francisco, California to Miami, Florida.

胡佛大坝高726英尺，底部厚660英尺，包含足够的混凝土铺就从加利福尼亚州旧金山到佛罗里达州迈阿密的双车道公路。