In a freaky twist of the calendar, a new bridge to provide a safe haven for bats has just opened days before Halloween in a Dutch town called ... Monster.

"The aim is that the bridge can act as a shelter for four different kinds of bats at different points in the year," Bart Reuser, from the firm Next Architects, told AFP.

Spanning some 25 metres (yards), the overpass has been built at a cost of some 700,000 euros (772,000 dollars) out of concrete "which keeps the heat in winter" and "is not too hot in summer."

Nicknamed the "batbridge," it snakes over a small canal and has been specially constructed with numerous cavities in which the flying mammals can hunker down to hibernate or reproduce.

The Netherlands boasts some 20 different kinds of bats, all protected since 1973, according to Dutch experts. But across Europe the creatures have been increasingly endangered by a loss of habitat.

Opened in the western Dutch town of Monster, the bridge is situated along a flight path commonly used by bats.

Cars and traffic are banned. Only cyclists and pedestrians will be able to cross the bridge in order not to disturb the bats from their sleep.

A large cavity dug at the bottom on one side will provide a bunker-like shelter during winter, while deep cavities cut into the underside of the bridge offer shady hiding places in the summer.

The bats will also be able to snooze safely out of reach of prowling cats who will be deterred by the water.

Built as part of a project by local authorities to create a green recreational park, Reuser said it would be a while before the first bats take up residence.

As for the date of the bridge's opening, just before legions of ghosts and vampires are due to stalk the streets? It's merely a coincidence, and "not at all intentional," said Reuser.

In fact, Halloween is not widely celebrated across the Netherlands.