By Lynn Schnaiberg

Long-ago explorers like Ferdinand Magellan or David Livingstone helped piece together maps of the planet. But these days, it seems like no patch of land has been left unexamined. As these recent discoveries prove, plenty of secrets still remain hidden for modern-day explorers to unearth and share with the rest of us.

Cancuen, Guatemala.
This will teach you to watch where you walk. Archeologists who in 2000 discovered what is billed as one of the biggest, most remarkable palaces built by Mayan kings literally stumbled upon this site while walking atop top a jungle-coated hill. The hill turned out to be a three-story palace complex stretching across the equivalent of two football fields. In this little-known ancient city known as the "Place of Serpents," limestone walls wind around 11 courtyards and through 170 rooms dating from the eighth century A.D. Thought to have been a powerful and prosperous trading hub, this city tucked into the remote rainforest has already revealed huge amounts of jade and other precious items. It may take a decade to fully excavate, but Cancuen has already offered up a few surprises that may turn conventional wisdom about Mayan civilization on its head.

Herakleion and Menouthis, Egypt.
Talk about a two-fer. Scientists in 2000 found these 2,500-year-old sunken cities a few miles off Egypt's Mediterranean coast near Alexandria. Lodged in the sea floor in waters less than 30 feet deep, the find was replete with pristinely preserved houses, temples, colossal red granite statues, ceramics, Islamic and Byzantine jewelry, and coins. Until Alexander the Great founded Alexandria in 331 B.C., Herakleion served as Egypt's main commercial port--and the home of the Temple of Hercules. For its part, Menouthis drew pilgrims from across the Mediterranean to worship in temples to gods like the mighty Isis. Both cities are well-documented by such ancient writers as Herodotus and Seneca (who blasted them for their sinful ways). Experts think powerful earthquakes pushed both cities into the sea; sin apparently carried a steep price back then.

Calakmul, Yucatan, Mexico.
About one-third larger than Guatemala's Tikal (long regarded as the greatest Mayan site), Calakmul encompasses more than 6,000 Mayan structures stretching across some 20 square miles of jungle in the increasingly deforested Yucatan. Calakmul was discovered in the early 1930s with the help of savvy locals, but exploration didn't begin until 1982. A bounty of ceramics, glass, obsidian, masks, and jewelry--not to mention a 165-foot pyramid--have surfaced from the ruins.

Terra-Cotta Army, Xi'an, China.
Uncovered in 1974, three tombs produced what many call the greatest archeological discovery of the 20th century, and one that is still under excavation today. In a quest for immortality and eternal power, China's first emperor, Qin Shi Huang, chose to have himself buried with some 8,000 life-size, intricately carved soldiers, horses, and chariots. All stand guard to protect their erstwhile master. It took some 700,000 laborers about 36 years to build the monument, but what else would you expect from the guy who also gave China the Great Wall?

Tomb of the Lord of Sipan, Lambayeque, Peru.
Battling looters hoping to make a killing on the art market, archeologists in 1988 uncovered the tomb of the Lord of Sipan, since dubbed the King Tutankhamun of the Americas. The discovery on the plains along Peru's northern coast resulted in what many call the greatest haul of pre-Colombian antiquities ever unearthed, including goodies like a two-foot-wide solid-gold headdress and exquisitely wrought jewelry. So you see, sometimes the good guys do win.

Lynn Schnaiberg, a Chicago-based writer, is a regular contributor to iExplore.