A mystery crater that appeared at a beach in the French resort town of Nice has left residents scratching their heads. Some suggest the large, round crater is either a geyser or a volcano.

A sinkhole 5 meters in diameter and 2 meters deep, filled with brackish water, emerged on Lido beach in Nice, along the famous Promenade des Anglais, local media report. Locals were stunned by its perfect roundness. Some wondered what may have caused the phenomenon.

“It's either a volcano or a geyser,” one Nice resident told 20minutes outlet. Others suggested the crater was from “a meteorite.”

Un cratère spectaculaire se forme sur une plage de Nicehttps://t.co/JlEbX2phospic.twitter.com/T7gWowmcEt — BFMTV (@BFMTV) February 1, 2018

“The tram runs beneath [the place], and the ground moves down,” another local said.

Authorities say the hole, which began forming on Wednesday, doesn’t pose any danger to public safety.

“No worries, it's a natural phenomenon that happens four times a year. And for journalists – no, the tram did not make a detour,” Nice Mayor Christian Estrosi tweeted.

Pas d'inquiétude, c'est un phénomène naturel qui arrive 4 fois par an et pour les journalistes, non, le tramway n'a pas fait un détour 😉 pic.twitter.com/GZvY9okRxi — Christian Estrosi (@cestrosi) February 1, 2018

READ MORE: Moment of powerful sinkhole implosion caught on camera (VIDEO)

A few weeks ago, a similar sinkhole formed in the middle of a roadway in downtown Nice, near the underground tramline currently under construction, according to Paris Match.

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