ISIS militants pocketed up to $200 million last year on plundered antiquities from Palmyra, the Syrian desert town with 2,000-year-old ruins, Russian investigators revealed.

Palmyra is an archaeological gem and a cherished landmark known endearingly to Syrians as the "Bride of the Desert." It is also a strategic crossroads linking the Syrian capital, Damascus, with the country's east and the border with Iraq. Syrian forces recaptured Palmyra in March, their first major victory in years over Islamic State fighters who had overseen a 10-month reign of terror in the town.

During their stay, the extremists destroyed some of Palmyra's best-known monuments, including two large temples dating back more than 1,800 years and a Roman triumphal arch. The militants also used the ancient Roman amphitheater for public killings, including a video they released showing 25 boys with pistols shooting captured Syrian soldiers, with the colonnades in the background.

The militants reportedly reduced much of the ancient town to rubble. Drones sent over to explore the site found that little remains of the Temple of Bel, the Arc du Triomphe and the Fakhr-al-Din al-Ma’ani Castle.

Vitaly Churkin, Russia’s ambassador to the United Nations, said in a letter released Wednesday that the militants formed an antiquities division that monitored these transactions.

“The main center for the smuggling of cultural heritage items is the Turkish city of Gaziantep, where the stolen goods are sold at illegal auctions and then through a network of antique shops and at the local market,” Churkin wrote, according to Reuters.

Turkish officials did not respond in the Reuters report, which points out that the two countries have had strained relations since Turkey shot down a Russian jet last November. 

The Associated Press contributed to this report.