A National Geographic Explorer’s search for Cleopatra’s tomb got a big breakthrough.

Kathleen Martínez has spent the last 20 years searching for the lost tomb of Cleopatra. Her work is part of a new Nat Geo special called “Cleopatra’s Final Secret.”

Martínez’s theory is that because the Romans hated Cleopatra, the queen had her deceased body sneaked to the Taposiris Magna temple in Egypt through underwater tunnels for burial.

Her latest search took her and her team underwater where they discovered an ancient port submerged site miles offshore of Taposiris Magna in the Mediterranean Sea.

In the remarkable clip, seen in the video player above, Martínez called legendary National Geographic Explorer Bob Ballard, who discovered the Titanic, to share the news.

“I have a very big smile on my face,” Ballard told her. “There is an island with a harbor that has a tunnel leading from the temple, we think, to that very spot. This doesn’t get any better.”

“After 2,000 years nobody has ever been there,” Martínez told her team. “We are the first ones.”

You can read more about the fascinating discovery on nationalgeographic.com.

“Cleopatra’s Final Secret” premieres Sept. 25 on National Geographic and streams the next day on Disney+ and Hulu.

The Walt Disney Company is the parent company of National Geographic and this ABC station.