Jacob’s Well is one of the longest underwater caves in Texas. It’s basically a spring-fed pool that is made by the thousands of gallons of water per minute that surge up into the well. The well acts as headwaters to Cypress
The Baatara gorge waterfall.The Baatara gorge waterfall (Balaa gorge waterfall) is a waterfall in the Tannourine, Lebanon. The waterfall drops 255 metres ft) into the Baatara Pothole, a cave of Jurassic limestone located on the Lebanon Mountain Trail.
Fingal’s Cave, Inner Hebrides, Scotland. "Fingal's Cave is a sea cave on the uninhabited island of Staffa, in the Inner Hebrides of Scotland, part of a National Nature Reserve owned by the National Trust for Scotland" via Wikipedia.