The ancient Greek philosopher Plato once wrote that Atlantis — everyone's favorite lost island civilization — had been destroyed around 9,000 B.C. after its inhabitants attempted to take over Athens. Plato placed the island city-state near the modern-day Strait of Gibraltar, and claimed it "disappeared into the depths of the sea" in a single day and night, leading many to speculate that a tsunami destroyed it. Ever since Plato's tantalizing hints, many a treasure hunter has gone in search of Atlantis, but nobody has ever definitively located it. Here are four possible locations, starting with the latest theory:

1. Spain
This week, a U.S.-led research team announced it had pinpointed an ancient city it believes to be Atlantis. Using a satellite image of a submerged site near Cadiz, in southern Spain, the researchers used radar and data mapping to survey the area, which they believe was flattened thousands of years ago. "This is the power of tsunamis," head researcher Richard Freund told Reuters. Freund is particularly confident that he has found the genuine article because of his discovery of a series of nearby "memorial cities" built in Atlantis' image by refugees who had fled the sunken island. The team is presenting its findings on a Discovery Channel special this week.

2. Off the coast of Africa
In 2009, an engineer working with Google Ocean, the search engine's ocean-mapping tool, spotted a "network of criss-cross lines" about 620 miles from the northwest coast of Africa. The rectangular area, the size of Wales, looked a lot like the neat grid of a city, leading experts to wonder whether it could be a well-preserved Atlantis remnant. However, the National Oceanic and Atmospheric Administration debunked the idea, pointing out that the grid effect was caused by sonar waves.

3. Greece
Last year, Bettany Hughes at The Daily Mail theorized that Plato may actually have been writing a "moral fable" based on the island of Thera — modern-day Santorini, Greece — when he described Atlantis. Like the fabled lost city, Thera endured a horrific disaster (in its case, a cataclysmic volcanic eruption) that brought an end to its sophisticated civilization in a matter of days. Vulcanologists and archeologists are unearthing evidence of a "Pompeii"-like civilization under the current-day vacation spot. 

4. Cyprus
In 2004, American researchers said they had found evidence of the Atlantis site near Cyprus. Using sonar, team leader Robert Sarmast claimed to have found "massive, manmade structures" beneath the ocean, including two walls resting on a slope, which he claimed matched Plato's description of "Acropolis Hill." "Even the dimensions are exactly perfect," he said, as quoted by the BBC, "so if all these things are coincidental, I mean, we have the world's greatest coincidence going on."