In 1905, a 13-year-old boy, Ben Sands, stumbled upon a remarkable discovery deep within the Craighead Caverns in Tennessee.

The island of Kastellorizo holds a natural wonder that remains one of the country’s best-kept secrets: the Blue Cave.

But the escalating trade war between the U.S. and China is now crippling an entire industry that hand-harvests geoducks, ...