The painting, which shows the sea lapping against a beach, dates from 1882
A Monet painting, which was stolen from a Polish museum and replaced with a copy painted on cardboard, has been recovered almost a decade later.
Police said they found Beach in Pourville, valued at $1m (£613,586) when it was taken in September 2000, in the southern Polish city of Olkusz.
Police have also arrested a 41-year-old man in connection with the theft of the Impressionist work.
He faces up to 10 years in prison if convicted.
Poznan police spokesman Romuald Piecuch said the recovered painting had been taken to the National Museum in Poznan, where experts intend to verify its authenticity.
"We have great hope that it is our stolen painting," museum spokeswoman Aleksandra Sobocinska said.
Ms Sobocinska said she did not have an estimate of its current value, but added that "to us it was a priceless masterpiece".
The 1882 oil study of a beach in northern France was the only Monet on public display in Poland.
The theft was discovered on 19 September 2000. It had been cut from its frame and replaced it with a copy.
Investigators have long been trying to trace a man who was seen making sketches of paintings in the museum two days earlier.