Could it contain the remains of ancient Greek leader Alexander the Great, or (less appealingly) a deadly curse?
According to experts who have now unsealed it, it's a no to both.
Instead, it revealed three skeletons and red-brown sewage water, which gave off an unbearable stench.
Egypt's Ministry of Antiquities had appointed a committee of archaeologists to open the relic, which was unearthed at a construction site.
According to Egyptian news outlet El-Watan, they initially lifted the lid of the tomb by just 5cm before the pungent odour forced them from the inspection scene entirely. They later prised it open with help from Egyptian military engineers.
"We found the bones of three people, in what looks like a family burial... Unfortunately the mummies inside were not in the best condition and only the bones remain," said Mostafa Waziri, secretary-general of the Supreme Council of Antiquities.
Addressing media fears that disturbing the tomb could trigger an implacable Pharaoh's curse, Mr Waziri declared: "We've opened it and, thank God, the world has not fallen into darkness.
"I was the first to put my whole head inside the sarcophagus ... and here I stand before you... I am fine."
Despite that, the site has now been cleared of people amid fears the sarcophagus could release lethal toxic fumes, Egypt's state-owned newspaper Al-Ahram says.
Experts have said the three individuals in the tomb may have been soldiers in the time of the Pharaohs.
The skull of one is said to show cracks which point to an arrow injury.
An alabaster bust, its features weathered beyond recognition, was also found with the sarcophagus.
The structure is almost two metres high and three metres long, and is the largest of its kind ever found intact.
It weighs in at 27 tonnes, and is believed to date from the early Ptolemaic period, which began in 323 BC after the death of Alexander the Great.
Archaeologists will now study the tomb in depth to pinpoint when its occupants lived, and how they died.