updated 4:49 p.m. ET Oct. 30, 2006

PARIS - 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."

It begins before midnight down a cobblestone side street just outside Paris' northern border. A small crowd, jittery like children off to summer camp, gathers behind an iron gate that opens onto a vast rail yard: a messy stack of rail ties, wood and machinery.

If You Go SIGNING UP: Tours for 2006 are already full, and dates for 2007 have not yet been announced. The best way to book is to sign up for the mailing list on the ADEMAS Web site, http://ademas.assoc.free.fr, or to become a member of the association for $31. COSTS: A ticket will cost $57. Along with the ticket, the association will send a detailed map with directions on how to get to the rail yard. WHAT TO BRING: Wear comfortable clothing, and bring a flashlight and a bottle of water. Drinks and snacks are available for purchase at the bar. LANGUAGE: Tours are conducted in French, at least until demand for English-language tours grows. Groups can arrange to bring along a translator.

"Tickets! Tickets, please!" a man calls from a rickety table.

The guides, railway enthusiasts from ADEMAS, explain historical changes in voltage, and how different types of wheels connect to the rails. (If a rubber tire goes flat, there's a smaller iron wheel behind it that will take over.)

Some people take notes, some take photographs, and many glance over their shoulders at the large clock in anticipation.

It's almost midnight. The Metro is about to close, clearing its tunnels of trains and making way for the tour. The night travelers clamber on to the brilliantly green Sprague-Thomson car, a vintage model from 1930.

On board, there are polished wooden bench seats and enamel decoration in cream, mustard and burgundy. Original maps showing Line Two stops and streets are posted overhead, and iron baskets hang above the seats for small luggage.

Slide show   Paris: City of delight It's a city of cafes and palaces and conversations. It's the City of Love - and more. more photos

A sign above the seats informs passengers that smoking and spitting are prohibited - a nod to modern day mores.

After the Metro's creation for the Universal Exposition of 1900, lines spread throughout the city. The insignia decorating the doors of this train bear the initials CMP, one of the two Metro companies that competed for customers before World War II.

The train departs with a jolt that surprises a few passengers. They smile nervously and grip the seat backs, laughing as high-pitched whirring and chugging noises accompany the train into the city's underground tunnels.

MORE FROM EUROPE TRAVEL

Europe Travel Section Front

Rome: Glimpse of eternity in a mere 2 days Bargain Britain? If you know where to look Europe: By plane or by train? 48 hours in the heart of Tuscany's wine country Best English country retreats Europe's top 10 best places to live Paris tourism on rise despite economic woes Europe's under-the-radar spots No sandcastles please, you’re in Italy More Americans check into European hostels Europe Travel Section Front   Add Europe Travel headlines to your news reader: