Keen observers had spotted what appeared to be the outline of a vast city on the floor of the Atlantic Ocean.

But the criss-crossing lines, located 600 miles west of the Canary Islands, were today explained by Google as sonar data collected as boats mapped the ocean floor.

A spokeswoman said: "It's true that many amazing discoveries have been made in Google Earth including a pristine forest in Mozambique that is home to previously unknown species and the remains of an Ancient Roman villa.

"In this case, however, what users are seeing is an artefact of the data collection process.

"Bathymetric (or sea floor terrain) data is often collected from boats using sonar to take measurements of the sea floor.

"The lines reflect the path of the boat as it gathers the data.

"The fact that there are blank spots between each of these lines is a sign of how little we really know about the world's oceans."

The network of criss-cross lines had been spotted 620 miles off the coast of north west Africa near the Canary Islands on the floor of the Atlantic Ocean.

The perfect rectangle was noticed on the search giant's underwater exploration tool by an aeronautical engineer who claims it looks like an "aerial map" of a city.

The underwater image can be found at the co-ordinates 31 15'15.53N 24 15'30.53W.

Google Ocean, an extension of Google Earth, allows web users to virtually explore the ocean with thousands of images of underwater landscapes.

Launched earlier this month, it lets users swim around underwater volcanoes, watch videos about exotic marine life, read about nearby shipwrecks, contribute photos and watch unseen footage of historic ocean expeditions.

The legend of Atlantis has excited the public imagination for centuries. In recent years "evidence" of the lost kingdom has been found off the coast of Cyprus and in southern Spain.

Plato described it as an island "larger than Libya and Asia put together" in front of the Pillars of Hercules - the Straits of Gibraltar. He said Atlantis was a land of fabulous wealth, advanced civilisation and natural beauty destroyed by earthquakes and floods 9,000 years earlier.

Source: Telegraph.co.uk