An ancient Italian city destroyed by Attila the Hun and now hidden underground has been mapped for the first time via infrared photography, officials said.

Infrared aerial photography, combined with 3D reconstruction techniques, has revealed Altinum's spectacular coastal architecture, complete with bridges, walls, canals, houses and large public buildings, the Italian news agency ANSA reported Saturday.

"Until now we only knew that Altinum was there, we didn't know what it was like," team leader Paolo Mozzi said.

Writing in the journal Science, Mozzi said the maps show the existence of a complex urban structure and how inhabitants adapted to life on a lagoon.

The maps suggest the Romans exploited the watery environment centuries before the city of Venice began to emerge on the archipelago in the middle of the lagoon," he said.

Attila the Hun's army destroyed Altinum in 452 AD, with many of the city's residents fleeing the lagoon islands that later became Venice.