It's known as the City of Light, but Paris has taken a dizzying step towards being the City of Fright after the Eiffel Tower unveiled a new glass floor.

Offering dramatic views of the 57-meter (187-foot) drop from the 125-year-old landmark's first level, the transparent walkway has already proved a hit with visitors lining up -- and lying down -- to take selfies.

Paris's mayor, Anne Hidalgo, opened the new attraction saying it would help bring back some magic to a city that's been criticized for disappointing foreign visitors.

"I hear that Paris has lost its shine and attractiveness," she said. "It's not true."

The new floor, she added, proved Parisians could re-invent their city "without ruining our history."

It's the latest in a series of glass floored walkways to open in prominent destinations around the world. These include Chicago's Willis Tower Skydeck and the Grand Canyon Skywalk.

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'Breathtakingly high'

Hidalgo celebrated the opening with a series of multi-lingual tweets inviting tourists to "enjoy this breathtakingly high experience."

The glass floor is part of a $38.4 million renovation of the tower's first floor that also includes shops, restaurants and a museum.

New outward-curving safety barriers also allow better views over the city.

Until now, the tower's somewhat gloomy "premiere etage" has been one of its least visited areas, with most of its seven million annual visitors heading straight to higher levels.

Built by Gustave Eiffel, the Tower was completed in 1889 as part of a "Universal Exposition" celebrating the centenary of the French Revolution.

At 312 meters, it was the tallest building in the world until New York's Chrysler building overtook it in 1930.

It was originally designed as a temporary attraction, but the decision was made to keep it as a permanent attraction -- and the Tower has never looked back.

Thanks to the glass floor though, it can now look down.