These mysterious geometric patterns have appeared in fields around Leamington.
Farmer Les Evans discovered a 16-metre crop circle in his field next to Chesterton windmill last Friday and then a key design materialised overnight.
He said: "They have trampled quite a lot of crops, but I have got no problem with it.
"One now and again generates quite a bit of interest.
"It's very clever what someone has done and very artistic.
"There are theories going around about who has done it.
"Maybe the aliens or the Romans have come back as aliens to keep an eye on the Roman town there. But I think we all know it's students."
Julie and Brian Branston of Southam contacted the Courier after spotting a crop circle on their way to work on Monday.
The circular marks can be seen in field on the left of the A425 going up the hill from the Fosse Way towards Radford Semele.
Mrs Branston, 42, who works at Warwick Hospital, said: "It was quite a shock. I have never seen any crop circles round here before.
"We thought 'someone's having a giggle'. I don't believe in aliens.
"There are tractor tracks running up the field so whoever did it could have used those to make sure they didn't leave any marks.
"They do look quite good, like a clock face with others around it decreasing in size."
Mrs Banston said the circles were not in the field on Friday, but a friend from Stockton saw them on Saturday morning.
Anyone wishing to see the crop circles near Chesterton windmill should follow a path that has been created.