An older article with some more details: https://www.news-leader.com/story/news/business/2015/03/16/springfield-underground-rare-vacancy/24834597/ https://www.

An older article with some more details: https://www.news-leader.com/story/news/business/2015/03/16/springfield-underground-rare-vacancy/24834597/ https://www.news-leader.com/story/news/business/2015/03/16/s... It's about 5 million square feet, or 115 acres. An even larger facility is in Kansas City: https://www.bloomberg.com/news/features/2015-02-04/welcome-to-subtropolis-the-business-complex-buried-under-kansas-city https://www.bloomberg.com/news/features/2015-02-04/welcome-t...