The find, which could provide insights into one of the Bible's most reviled yet influential figures, includes hundreds of pieces of an ornate sarcophagus, but no bones and no inscription that would seal the identification.
Although the tomb was shattered and empty, leaders of the Israeli team that unearthed it said Tuesday they will dig on in the hope of finding jewelry, other artifacts or even the biblical monarch's remains.
Hebrew University archaeologist Ehud Netzer said he has been leading the search for Herod's tomb at the king's winter palace in the Judean desert, in an Israeli-controlled part of the West Bank south of Jerusalem, for 35 years.
Last month, his team started unearthing limestone fragments, from which emerged the picture of an ornately carved sarcophagus with decorative urns of a type never before found in the Holy Land.
"It's a sarcophagus we don't just see anywhere," Netzer told reporters at the university. "It is something very special."
The complete sarcophagus would have been about nine feet long, the university said.
Herod was the Jewish proxy ruler of the Holy Land under imperial Roman occupation from 37 B.C. His most famous construction project was expanding the Jewish Second Temple in Jerusalem.
Remnants of his extensive building work in Jerusalem are still visible in Jerusalem's Old City, and he undertook major construction projects in Caesaria, Jericho, the hilltop fortress of Masada and elsewhere.
At the excavation site, on the steep, rocky slopes of a cone-shaped hill 2,230 feet high, Netzer's assistant, Yaakov Kalmar, said that an account of Herod's funeral by the first-century historian Josephus Flavius left little doubt that it took place at Herodium. The newly discovered tomb was regal in its opulence.
"We have here all the attributes of a royal funeral," Kalmar said. "We didn't find inscriptions so far... The work is not finished."
The site sits halfway up the hill, atop a warren of tunnels and water cisterns built to serve the palace at the summit.
Stephen Pfann, an American expert in the Second Temple period at the University of the Holy Land, called the find a "major discovery by all means," but said the lack of an inscription hindered full verification.
"We're moving in the right direction. It will be clinched once we have an inscription that bears his name," said Pfann, who did not participate in Netzer's dig.
Eric Meyers of Duke University, who has excavated in the Holy Land, said initial descriptions of the tomb pointed to its authenticity as belonging to Herod.
"We know he was buried at Herodium," he said by telephone. "It's a significant find."
Meyers said that among key clues were that the sarcophagus was placed on a raised platform rather than in the underground tombs used for those of lesser rank, and that in accordance with Jewish religious law, it was not decorated with any human image.
"It sounds as if Herod was respectful of his Jewish tradition right up to the end," he said.