The at least 2,000-square-metre building was part of the Kingdom of Mitanni, an ancient state that ruled most of Syria and Anatolia, according to the University of Tuebingen.

After making the discovery last autumn, archaeologists had only three weeks to examine the building before water levels at the reservoir rose again.

"We dug as fast as we could," Ivana Puljiz, a senior archaeologist from the University of Tuebingen, told dpa. As water levels rose, the building vanished completely again. The walls, made of clay bricks, are up to two metres tall and inside archaeologists found mural paintings in glowing red and blue colours. It was an "archaeological sensation," Puljiz said, explaining that these kinds of paintings are rarely found.

Ten cuneiform scripts were also found inside the building. One of them indicated that the palace was once part of the old city of Zachiku, Puljiz said.

The site belongs to the Kurdish autonomous region in northern Iraq. According to the university, Kurdish archaeologist Hassan Ahmed Kasim considers the discovery to be one of the most important finds in the region in recent decades.

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