Cairo - Egyptian authorities announced on Monday the discovery at Cairo's citadel of an underground passageway tall enough to accommodate a mounted horseman.
The 150-metre-long tunnel, the longest of several beneath the citadel, was found in the vicinity of the 19th century Mohamed Ali mosque in the course of a project to drain off groundwater from under the compound.
The Cairo Citadel dates to the 12th century. The much newer Mohamed Ali mosque, one of several buildings on the compound, is a major Cairo landmark visible from several vantage points around the city.
The narrow passageway, which runs three to seven metres beneath the ground at different points along its length, appears to have connected palaces dating to the late 13th and early 14th centuries.
The passage, the age of which has yet to be determined, is blocked at one end by a wall that presents a modern mystery for antiquities officials who say it appears no older than 50 years.
Officials will study whether removing the wall could have an adverse effect structurally before making any decision to do so.
Experts participating in Napoleon's late 18th century expedition to Egypt mapped out several passageways beneath at the citadel, but so far antiquities officials are uncertain if the new discovery was one of them.
According to Mustapha Hassan, an official at the department for citadel antiquities, a number of passageways were filled in during the 19th century ahead of the construction during that era. - Sapa-dpa