Construction workers laying the foundation of a new garden bar at the landmark Sofitel Legend Metropole Hanoi this summer struck the roof of a long-buried air raid shelter, initiating a fevered disinterment and rediscovery of an all but forgotten piece of the hotel's wartime history.

After excavating more than two metres of earth and reinforced concrete and then jack-hammering through a 278 -millimetre ceiling, the hotel opened the hatch on a warren of flooded corridors, chambers and stairways.

In August, the hotel's general manager, Kai Speth, and his chief engineer dropped through a square metre-wide hole bored into the ceiling, illuminating a subterranean space of nearly 40 square metres.

They found an old wine bottle, a still-intact light bulb, air ducts, graffiti and eerie echoes of a war that ended almost four decades ago and that raged all about this shelter during the Christmas Bombings in 1972.

"In the hotel's history, we have a story of the American folk singer, Joan Baez, who sought shelter in this bunker during the Christmas Bombings, and who sang some songs beside a Vietnamese guitarist," said Speth. "We've always known a bunker was here, somewhere in the garden between the pool and the Club Bar, but looking for this wasn't even on our radar screen until my chief engineer tried to sink pilings for the new Bamboo Bar."

The hotel is still undecided about how best to utilise the underground space, but Speth is determined to make something of this novel asset, if only as a museum that shines a light on the ways and means of Vietnamese resistance during the war.

Today, in a traveler's destination that still reverberates with 'Good Morning, Vietnam,' some of the country's most compelling attractions involve underground exploration. In Cu Chi outside Ho Chi Minh City, tourists burrow through short passageways of an underground tunnel complex that sent tentacles through 200 kilometres of earth. Further north near the old Demilitarised Zone (DMZ), travellers explore the tunnels at Vinh Moc, where an entire village relocated as a hedge against American bombs.

The Metropole's shelter, though far less ambitious than either of those wartime developments, is nevertheless bound to stand among them as an emblem of Vietnam's travails.

"We don't know of any other hotels, in Vietnam or anywhere else for that matter, that maintained shelters for guests and staff," said Speth. 

The Metropole's standing as a hotel in a war zone garnered feature play on the cover of Life magazine, April 7, 1967. The magazine features a row of manholes, about 1.5 metres deep that line a sidewalk outside the hotel. Those manholes did not connect to the hotel's more spacious shelter but testify to life in a city under siege by American aircraft.

Otherwise, the hotel's connections to its most spartan chambers are thin. If there were records kept of the hotel's activities during the war, they're gone now. Speth recalls speaking once to a Canadian diplomat who told him he'd spent time in the shelter during the war.

Otherwise, references to the shelter have been shrouded by speculation. To wit, the hotel's somewhat foreshortened swimming pool has long been thought to be a consequence of an underground shelter.

The questions, now that that shelter has been opened, are only deepening. For example, who exactly was Bob Devereaux, who inscribed his name in cement on the wall of the shelter on Aug. 17, 1975? Is that when the shelter was sealed up?

Before that first trip underground, it took one full week of non-stop pumping before the water level could be brought down to 20 centimetres. Speth waded in then, wearing shorts, rubber boots and an old t-shirt, an outfit he's donned several times now as he's made additional excursions.

"I've worn a suit and tie for thirty years in my day-to-day as a hotelier, and I expect I probably will for the next 15 or 20 years, as well," he said. "But now, there's this chance to work some like Indiana Jones, and who can resist that?