An ancient city, which has previously been unknown, has been revealed on mainland Greece near the city of Vlochós to the north of Athens. British archaeologists found the city which dates back to 500BC.

Bournemouth University experts have been exploring the remains of a secret Greek city, which is said to be around 2,500 years old. They used drones to map the features of the ground, such as city walls, and a magnetometer and ground penetrating radar to investigate buried features, including the city's cobbled streets.

The researchers were exploring the ruins of Vlochós on the Strongilovoúni hill when they came across the remains of towers, walls, and city gates belonging to an ancient civilization. After a closer look, the team realized that they were indeed standing on the site of a former metropolis.

The city is too large to have gone unnoticed for so long, but this is only because it was too big to see from the ground, study author, Robin Röinland of the University of Gothenburg told IBTimes UK.

"It's a bit tricky to get an overview of the site without aerial photos or GPS - it's hard to see how various towers and gates relate to one another," Rönnlund says. "It's simply too much to grasp from the ground."

The researchers plan to use radar to view the subterranean relics, instead of excavating, and this is a fascinating part for Röinland. The land on the surface is inconspicuous field of thistles and brambles. "The domestic part of the city, where people lived, is covered by a thick layer of silt from a nearby river," Rönnlund said.

The researcher requires further archaeological investigation at the site, and this will shed light on the reasons why the city was abandoned. The experts will also be able to estimate the population of the city.