An ancient water tunnel was recently discovered by a group of tour guides in Jerusalem, and is believed to date back to biblical times.

The tunnel was uncovered by Israeli guides on a trip planned by the Etzion Field School. It measures 740 feet and sits just east of the security barrier between Israel and the West Bank.

Yaran Rosenthal, head of the school for the Society for the Protection of Nature in Israel, said the tunnel likely predates 568 BCE, and is one of the longest ever found in Israel.

“We entered a 15-foot shaft through a very narrow entrance and headed eastward underground,” Rosenthal said.

“We were amazed at the beauty of the structure we were in, whose corridor is built from huge slabs of more than a cubic yard. At the end of this construction, a simpler path begins and a neat staircase leads to that part.”

The structure, which is within Jerusalem’s municipal boundaries, has a ceiling that varies in height between five and nine feet. It is also two to three feet wide.

Rosenthal added that markings on the tunnel indicate it might have been owned by a Judean king.