In 1927, New York opened the Holland Tunnel with an innovative ventilation system; 84 fans still move air through its 8,500-foot twin tubes

Nearly a century after opening, the Holland Tunnel's original ventilation system, 84 fans across four buildings, still keeps drivers safe from carbon monoxide. Built between 1920 and 1927, its "transverse" airflow design became the model for tunnels worldwide. A decades-long health study on tunnel officers found real but manageable risks. Today, over 30 million vehicles a year pass through, unaware of the century-old engineering working above them.