URL：https://strangesounds.org/wp-content/uploads/2014/03/Bottomless-Pit-at-The-Monticello-Dam-in-California-is-the-dam-drain-hole.jpg
掲載元：https://strangesounds.org/2014/03/uk-sinkhole-formation-huge-sinkhole-drains-pond-within-hours-in-stockport-park-near-london.html
