Weather experts are baffled by the appearance of a black ring in the sky above Leamington Spa on Friday evening.
Schoolgirl Georgina Heap was playing tennis with her mother Jo Heap when she saw the mysterious black ring in the sky near Warwick Castle.
The ring remained in the sky for around three minutes before disappearing completely.
Miss Heap, who is studying for her GCSEs, described the circle as "the weirdest thing I have ever seen."
"I looked up at it and thought 'what the hell?', it was amazing," she said. "It was just floating there like a cloud and then it disappeared. It wasn't birds either. There were about ten of us who stopped what we were doing and watched."
The 16-year-old photographed the circle on her iPhone but so far, experts have been un able to offer explanation for the unusual sighting.
While the circle resembles a giant smoke ring, Warwickshire Fire and Rescue service said that there had been no reports of a fire in the locality at the time of the sighting.
The Met Office said that the ring did not appear to be weather-related.
Nick Pope, an expert on UFOs and a previous government adviser on unexplained phenomena, said he believed the circle to be 'organic'.
"It's a truly bizarre image. It looks like a smoke ring, but I can't see where it could have come from. Other alternatives would include some sort of unusual meteorological phenomenon," he explained.
"One other possibility is that the shape is made up of millions of bees or other insects, but I've never heard of insects behaving in this way before, so if this is the explanation, it's a real-life X-File."