You loved our first installment of the world's most mysterious places, so we went back out to dig up more. From ocean floors to crystaline caves, here are 10 more places that will make you want to buy a ticket, pack your bag and see the world.
Maunsell Army Forts, Kent, England
These still-standing remnants of World War II are just off the coast of Kent, England. Now abandoned, they can be seen from land on a clear day, but you'll need a boat to get a good look. In the 1960s and '70s, they were famously taken over as pirate radio stations, and a nearby similar construction became the self-proclaimed island nation known as the Principality of Sealand – although no other country actually acknowledges them as a sovereign nation.
Fly Ranch Geysers, Nevada, USA
While this might look like a natural wonder, technically it's not. This sort of man-made water geyser was created when an oil well was left improperly sealed, which let minerals deposit on the ground and eventually built the geyser seen here. It's small (only about 5 feet tall) but is still growing. The wicked colors? Thank the thermophilic algae present in the water.
Reed Flute Cave, Guangxi, China
Buried deep underground in southeast China is this natural wonder, the Reed Flute Cave. The name doesn't come from the stalactities but from the reeds outside the cave, which can actually be made into flutes. The cave has been a tourist attraction for a number of years – inscriptions inside date back more than 1,000 years. As for that incredible light? Sadly, it's artificial.
Crater Lake, Mount Katmai, Alaska, USA
Sitting at 6,716 feet atop Mount Katmai in Alaska isn't a peak, but a hole. Filled with water, it's affectionately referred to as "Crater Lake." (There are a few other Crater Lakes out there.) What's unique about this one? The rim of the volcanic mountain is just over 6,716 feet, but the lake sits approximately 2,496 feet below, making for one heck of a high-dive. Good thing the lake is thought to be almost 984 feet deep. (Warning: Attempting an actual dive here is not a good idea, unless you're wearing a wingsuit.)
USS Kittiwake shipwreck, Cayman Islands
The USS Kittiwake was built in 1945 and served the U.S. Navy for almost 50 years as a submarine rescue vessel. Now, the ship is a submarine itself – sitting on the ocean floor as an articificial reef in the Cayman Islands. It's one of the best shipwrecks in the world for diving, attracting SCUBA enthusiasts from all over the world. You'll want to spend a lot of time down there – the ship is over 250 feet long.
Read about more the best places for wreck diving
Vila Franca do Campo, Azores Archipelago
The Portuguese Azores islands are formed from volcanic rock in the middle of the Atlantic Ocean. Once connected to the legend of Atlantis, the islands are now a stop in the Red Bull Cliff Diving competitions. The divers leap from 90 feet above the water, performing a series of maneuvers before splashing down into the Atlantic. The islet pictured here operated as both a winery and a military base before being declared a nature reserve.
Dzitnup Cenote, Yucatán Peninsula, Mexico
A "cenote" is a sinkhole, often with a fresh water pool at the bottom. The Yucatán Peninsula is famous for them, and the Dzitnup is one of the most famous of all. There are an estimated 3,000 cenotes on the Yucatan Peninsula, mostly undocumented, and a 99-mile underground river. You can check out the cavern and its dripping stalactites for yourself – the locals treat it like the community pool (and yes, you have to buy a ticket).
Petra Treasury, Jordan
You've probably seen pictures of the famous Petra Treasury in Jordan, but this one is worth a second look – candles light up the foreground at night in front of the milleniums-old building in the rock. Wanna visit? You might have to make a journey like this to get there.
Shilin Stone Forest, China
Legends about the Stone Forest abound, but one that's wrong is that they are petrified trees – they're actually limestone. It's a world heritage site and is open for visitation. Prefer caves? Check out one of the world's largest cave systems.
Rio Tulija, Mexico
The Rio Tulija and the "Agua Azul" area in southern Mexico are known for their light blue water. It's a whitewater paradise for pro kayakers like Rafa Ortiz, who took a crew of his buddies for a ride they won't forget.