Coalition forces in Iraq have caused irreparable damage to the ancient city of Babylon, the British Museum says.
A double fortified wall enclosed the city, protecting it from attack
Sandbags have been filled with precious archaeological fragments and 2,600 year old paving stones have been crushed by tanks, a museum report claims.
The US Army says the troops based in the city, some 50 miles (80km) south of Baghdad, are well aware of its historical significance.
Babylon's Hanging Gardens were among the Seven Wonders of the Ancient World.
The legendary gardens featured water diverted from mountain streams cascading down artificial hills built upon stone vaults.
American troops occupied the site in April 2003, initially to protect it from looters and vandals.
John Curtis, author of the museum's report, said this was "tantamount to establishing a military camp around Stonehenge".
"About 300,000 square metres of the surface of the site has been flattened and covered with compacted gravel and sometimes chemically treated," he said.
"This will contaminate the archaeological record of the site."
He added: "I noted about 12 trenches, one of them 170m long, which had been dug through the archaeological deposits."
Mr Curtis, who is curator of the museum's Near East department, also found evidence of fuel leaks.
But US military spokesman Lt Col Steven Boylan said the base, which has around 6,000 troops under Police command, is needed to "further defeat terrorists and insurgents".
He told BBC Newshour: "Any of the excavations or earth work that we have done in order to do our operations... was done in consultation with the Babylon museum director and an archaeologist."
At the height of its power, Babylon was an awe-inspiring sight, with two sets of fortified walls surrounding massive palaces and religious buildings.
It became one of the most important cities in Mesopotamia, one of the cradles of human civilisation.
Iraq is home to 10,000 archaeological sites.