7 missing wonders of the world

With as many as 1,500 active satellites orbiting the Earth and the human population approaching seven billion, you'd think that everything of value on the planet would have been discovered by now.

But some of the world's most famous historical objects, from the Holy Grail of medieval lore to the wreckage of Amelia Earhart's plane, remain unaccounted for. Here is a list of seven missing treasures, compiled by the Wall Street Journal.

1. The Tomb of Genghis Khan

Historians say that the great conqueror died somewhere in northwest China during an expedition in 1227. But the exact burial site remains to be discovered. Maury Kravitz, a 78-year-old semiretired attorney and commodities trader from Highland Park, Ill., has spent 18 years and more than $4 million searching north-central Mongolia for the tomb of Genghis Khan.

2. San Jose, the sunken Spanish treasure ship.

Somewhere off the coast of Colombia lies the San Jose, a sunken Spanish galleon thought by some to be carrying more than $1 billion in treasure. The vessel went down 600 meters under sea in June, 1708, when an unaccounted explosion occurred as it was being chased by British warships.

3. The Amber Room of Russia

The Amber Room is a complete chamber decoration of amberpanels backed with gold leaf and mirrors, a gift from Prussian king Friedrich Wilhelm I to his then ally, Tsar Peter the Great of the Russian Empire in 1716. Due to its singular beauty, the room was sometimes dubbed the "Eighth Wonder of the World." The Baroque masterpiece was looted during World War II by Nazi Germany. Knowledge of its whereabouts was lost in the chaos at the end of the war.

4. Tomb of the Egyptian queen Nefertiti

The bust of Nefertiti, an Egyptian queen from 14 B.C., hailed as the perfect beauty, is one of the most valued Egyptian treasures. Although the bust can be appreciated by many through a Berlin Museum collection that possesses it, archaeologists are still searching for the queen’s tomb that will shed light not only on when and why the queen died but also the ancient Egyptian world.

5. Holy Grail

Holy Grail is a sacred receptacle, most often identified as a dish, plate, or cup used by Jesus at the Last Supper and said to possess miraculous powers. Although historians say that the grail is the result of human imagination, the frequent subject of films and fictions remains as one of biggest mysteries of mankind to many.

6. The Battle of Anghiari, a mural by Leonardo da Vinci

Since the middle of the 16th century, nobody has seen a mural by Leonardo da Vinci that many of his contemporaries considered his greatest masterpiece. The Battle of Anghiari (1505), at times referred to as "The Lost Leonardo,” depicts soldiers on horses engaging in a fierce fight. Originally drawn on the wall of Vecchio Palace, Florence, the masterpiece disappeared during the reconstruction of the palace.

7. Amelia Earhart, the legendary American female aviator

Roger "Woody" Peard, 53, of Lake Tahoe, Calif., believes Amelia Earhart's Lockheed Electra 10-E, which disappeared over the South Pacific in 1937, was downed by a midair collision and buried on a Japanese military base in the Marshall Islands. He is raising $30,000 to fund an expedition to use ground-penetrating radar to prove his theory. "Nobody believes me," he says.