A lot has been written about the mysteries surrounding the famous Bermuda Triangle, and I'm not going to get into all of it here. There's simply not enough space or time to cover every insane theory or what-have-you out there. I'm going to be focusing on the epicentre of the phenomena, which seems to be located around the island of Bimini in the Bahamas.
I'm going to assume you've all heard something about the Bermuda Triangle, since it's one of the most publicized paranormal phenomena out there. But a quick rundown: the Bermuda Triangle is a rather large area, encompassing most of the Bahama region, with the "points" generally given at Miami, the city of San Juan in Puerto Rico, and the island of Bermuda. Some reports extend it inland to connect with the Mapimí "zone of silence" in central Mexico. In any case, the area is littered with wrecked ships, crashed aircraft and mysterious disappearances. Explanations have ranged from exaggeration by authors, to methane bubbles, to alien abductions. Some of the more famous cases linked to it are the Flight 19 disappearance in which 5 Avenger torpedo bombers disappeared without a trace, and the USS Cyclops disaster of 1918 in which a coal ship carrying 306 crewmen vanished during a crossing bound for Saint-Nazare, France.
My focus for the purposes of this article will be the islands of Bimini and the surrounding area, a hotspot for anomalous energy fields, strange lights and wrecks (some of which can be attributed to the reefs ringing the island). It's also home to the famous Bimini Road, an unusual underwater formation bearing more than a passing resemblance to a paved road. A significant portion of the island of South Bimini is undeveloped tropical forest, surrounded by unusual magnetic and electrical anomalies. It's eminently possible to get lost in this forest even if you have a compass and knowledge of the area, as compasses spin out of control and the very forest seems to turn on itself in a great labyrinth. The reason for these anomalies is currently unknown, but I believe there is a correlation between the Bermuda triangle, the Devil's Sea in the Pacific, and the so-called "lost continents" of Mu, Lemuria and Atlantis.
Specifically, I believe all the legends refer to a single location or civilization, spanning from approximately 15,000 BCE to 9000 BCE. What wiped out this civilization is unknown, and nothing truly confirms it yet, but widespread evidence and legend support a highly-advanced group (or groups) on Earth prior to the standard date of civilization's foundation, approximately 4000 BCE in southern Mesopotamia (the city-state of Sumeria, in what is now Iraq). Evidence has been found all across the world of some form of Tier-1 civilization between the modern-day Tropics. Examples include the Olmec stone heads, the Pyramids, a number of technologies referenced in the Indian Mahabharata, and the Annunaki in Sumerian myth. This civilization may have been extraterrestrial in origin, as posited by many ancient astronaut theorists, but I'm inclined to believe in a primarily terrestrial origin. That's not to say we've not had contact with alien intelligences in the past (and even to today), but I think it's completely possible that somewhere humans advanced to a point beyond our technology level today in the period between the first evolution of Homo sapiens and the birth of civilization. How they achieved this is unknown, but I do believe in some form of external intervention, be it intentional or not.
This is where my theories start to diverge from both conventional science and paranormal research. The world's tropical regions seem to be a hotbed of unexplained phenomena, as well as immense breakthroughs in science (see: the Maya, discovery of the Chicxulub crater). I figure there's something to this. To cut straight to the point, I think that there have been either landings of extraterrestrial craft (or crashes) along the equator, or the intentional placement of relics from an as-yet unknown ancient civilization. Either way this would mean the remnants of advanced technology buried deep beneath our planet's surface. I personally favour the crash theory. The energy on impact of an extraterrestrial craft travelling at the immense velocities required for interstellar travel could easily embed a metallic vehicle into the bedrock, and this is assuming the thing was conventionally propelled. The force of the impact would have thrown any and all systems aboard the craft out of alignment or what-have-you, and something this advanced could easily present as an electromagnetic anomaly. Assume the involved craft was absolutely massive, and struck at a sharp angle. For all we know, the disappearances could be a malfunctioning wormhole system (or any other reality-warping device). Detecting anything buried could be difficult, however. Unless there's a significant difference in density or other physical properties between the craft and the surrounding stone, it would be almost intangible. Getting to it (assuming that's an option, and not a madman's plan) is another story entirely. If we knew exactly where to begin, excavating the craft would be (from a technological standpoint), eminently feasible. It would be immensely expensive and would require the cooperation of many nations, but the payoff would be immeasurable. I'm almost sure this was in a movie at some point, but realistically all that would need to be done is locate the craft, drill a hole down to it, and work up.
As an extension to this, I believe that there are a number of locations around the world where objects of great value historically and technologically are deeply buried beneath the earth. It would certainly explain a lot.