Madrid is a completely landlocked city over 300km from the nearest coastline, so it came as some surprise when a dolphin was discovered in the centre of the city on Tuesday.
The animal's corpse, which was covered in metal chicken wire and in an advanced state of decomposition, was discovered by a dog-walker in Madrid's Casa de Campo - a park in the centre of the city.
The dogs made the discovery at around 3.20pm on Tuesday next to a cycle path running through the park, which is popular with joggers, cyclists and dog walkers.
Madrid police published a photo of the dead mammal on Twitter, writing that it was a cetacean, the first analysis pointing towards it being a dolphin.
The decomposing cadaver measures around one and a half metres in length.
But experts are scratching their heads over the provenance of the decomposing mammal after police confirmed that it did not come from Madrid Zoo - located in the park - which stated it was not currently missing any animals.
"We've never seen anything like this in the park," Francisco Rodríguez Pachón, who runs the park, told Spanish daily El País.
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The environment department of Madrid police has opened an investigation to determine where the animal came from.
Its body has been taken to Madrid's Animal Protection Centre where tests will confirm the species of the animal and how long it has been dead.