Stalagmites happen when water running down inside of the Earth picks up lime and drips down from the ceiling of a cave at the same place every single time. The drops evaporate and the lime builds up and forms the stick you see.
Texas is blessed with some of the nations most interesting "show" caves and thousands of "wild" caves throughout the state. Because of the varying geographical regions and features of Texas, you could literally tour the entire state by jumping from cave
This is an amazing shot. I love it. But I have a "thing" about plants and trees under water. Creeps me out! Such an amazing photo tho. (Anacapa Arch, Channel Islands National Park, California Photo by Antonio Busiello)
Ice cave in the Skaftafell National Park in Iceland. Ice caves collapse and new ones form as each glacier grinds slowly towards the sea. Local guides can help you (without dying) find one. (Visit Skaftafell National Park in Iceland.