JERUSALEM - Underneath the crowded alleys and holy sites of old Jerusalem, hundreds of people are snaking at any given moment through tunnels, vaulted medieval chambers and Roman sewers in a rapidly expanding subterranean city invisible from the streets above.
At street level, the walled Old City is an energetic and fractious enclave with a physical landscape that is predominantly Islamic and a population that is mainly Arab.
Underground Jerusalem is different: Here the noise recedes, the fierce Middle Eastern sun disappears, and light comes from fluorescent bulbs. There is a smell of earth and mildew, and the geography recalls a Jewish city that existed 2,000 years ago.
Archaeological digs under the disputed Old City are a matter of immense sensitivity. For Israel, the tunnels are proof of the depth of Jewish roots here, and this has made the tunnels one of Jerusalem's main tourist draws: The number of visitors, mostly Jews and Christians, has risen dramatically in recent years to more than a million visitors in 2010.
But many Palestinians, who reject Israel's sovereignty in the city, see them as a threat to their own claims to Jerusalem. And some critics say they put an exaggerated focus on Jewish history.
A new underground link is opening within two months, and when it does, there will be more than a mile (two kilometers) of pathways beneath the city. Officials say at least one other major project is in the works. Soon, anyone so inclined will be able to spend much of their time in Jerusalem without seeing the sky.
On a recent morning, a man carrying surveying equipment walked across a two-millennia-old stone road, paused at the edge of a hole and disappeared underground.
In a multilevel maze of rooms and corridors beneath the Muslim Quarter, workers cleared rubble and installed steel safety braces to shore up crumbling 700-year-old Mamluk-era arches.