To ensure its smooth operation, the MRT hides many "mysterious mechanisms," including a facility that resembles a vault door. 

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Curious commuters recently noticed a massive, vault-like door near exit 5 of Taipei Metro’s Nanjing Fuxing Station, sparking online speculation about its purpose. Taipei Rapid Transit Corporation (TRTC) clarified that the heavy, sealed structure is a flood barrier system, a vital defense mechanism designed after the devastating floods caused by Typhoon Nari in 2001.

During that storm, floodwaters inundated the blue Bannan Line and even swamped Taipei Main Station, reaching depths of up to 2.3 meters. The disaster led TRTC to design and install multiple waterproof systems across the network. “If flooding threatens, this watertight door, 30 centimeters thick, can be closed to prevent water from entering the platform level,” said CTS reporter Chang Hsiao-yuan (張小媛) while demonstrating the mechanism on-site.

According to Huang Yi-chao (黃怡超), a section chief from Taipei City’s Department of Rapid Transit Systems, the doors were introduced after engineers realized that flooding could easily overwhelm station entrances. “We decided to place basic waterproofing at entrances and add full-seal floodgates at station interfaces,” he explained.

TRTC uses several types of flood barriers, including swinging, vertical, and sliding models, to block water from penetrating underground areas. Although forecasts predict less rain from this week’s Typhoon Fung-wong than from Nari, with expected totals around 300 millimeters over two days, city officials said the metro system remains on high alert to ensure uninterrupted service.