PARIS, France (AP) -- An elderly couple waltzes to the steady carnival music of an organ grinder on the dingy platform of a Paris subway station. But it's nearly 3 a.m., and the station has been closed since World War II.

They are part of a traveling nocturnal party that barrels through the tunnels of the Metro long after the passenger trains have been tucked away for the night. These riders are on an exclusive, all-night Metro history tour, organized a dozen times a year by a group of railway buffs.

The ADEMAS association, dedicated to restoring old trains and preserving the Metro's history, has been around since 1992. (ADEMAS stands for Association D'Exploitation du Material Sprague; the Paris Metro's Sprague-Thomson model cars date to the early 1900s.)

But until recently, the group was as mysterious as the phantom stations they visit on their tours.

Rumors about the all-night Metro rides circulated by word of mouth and in Internet chat rooms, but details were almost impossible to track down -- until June, when ADEMAS launched its Web site. But even that lacks specific times and tour dates.

Association president Julian Pepinster says it's with good reason. There are just 2,400 spots available each year.

"There's a constant demand for the tours," he said in an interview. "Even with a dozen tours a year, there's always a six-month wait."...