In Syria and Iraq alone, UNESCO lists ten World Heritage Sites, and of those ten, they say, nine are presently in danger. ISIS, although not the only destructive factor, is definitely the main culprit.
The majority of the sites are located in Syria:
The well-preserved remains of Bosra on Syria’s southern border are less known but contain a great number of ancient buildings. Most famous is probably its Roman theater from the 2nd century AD, when Bosra was the capital of the Province of Arabia. Yet there also are many testimonies from the days when the city was ruled by the Nabataeans, the Byzantine Empire, and the Umayyads. Bosra, however, was one of the first cities under siege and suffering from repeated shelling and bombing by ISIS (the theater was a choice location for the snipers).
Lesser known but certainly as important are the so-called Dead Cities with their precious villages and churches that flourished between the 1st and the 7th centuries, ranging from antiquity to the end of the Byzantine era. Fighters and refugees alike sought shelter among these ruins, trying to accommodate the fragile remains to their needs.
From another time frame are the many Crusader Castles, the most renowned being the Crac-des-Chevaliers. They are unique because of their mixed architecture of European and Eastern influences. Here too, the Syrian army and the rebels occupied the premises in turn without any respect or consideration for the patrimony.
Last but not least, there is the damage done in Damascus, one of the most ancient cities in the world. Damascus was already a problem child because of a population decrease and people moving from older buildings to newer housing facilities. This left big gaps in some of the city’s neighborhoods. The fighting inside the Old City started as early as 2012 and caused more damage. UNESCO has counted as many as 125 protected monuments in Damascus, among which is the famous Umayyad Mosque, one of the largest mosques in the world.
UNESCO also lists a number of precious buildings in Iraq. Unfortunately, these are less known by the general public simply because traveling to Iraq was and is problematic.
The city of Hatra was one of the best surviving examples of a Parthian city founded in the 3rd or 2nd century BC. Most of its city walls and towers, as well as the sacred temenos of the Temple of Mrn, were still standing when ISIS arrived. As they did in nearby Nimrud a few days before, they hacked down the magnificent figures that decorated the arches and vaulted passages. The Great Temple was a rare example of combined Greek, Roman, Persian, and Arabian architectural styles.

The Assyrian city of Assur on the western bank of the River Tigris is another precious site, as it was the first capital of the Assyrian Empire. Assur existed for nearly four thousand years and was finally destroyed by the great Tamerlane. However, the stately Parthian Palace and Temple have survived into our 21st century until they fell under threat of ISIS. The fate of Assur remains uncertain, for if the city is not destroyed by terrorists, it may become a victim of the dam project on the Tigris, which will flood whatever walls that are still standing.
Finally, there is the old Abbasid capital of Samarra, which is the only surviving Islamic capital to show its original layout, architecture, and decorations (including mosaics and carvings). It is home to the Great Shiite Mosque, which was in danger when the city was taken by ISIS and was caught up in the war between Shiites and Sunnites. It seems that the Iraqi government was able to push the invaders back.
Not very uplifting altogether. As to Afghanistan, where the situation is far more complicated, there is the Valley of Bamiyan, where the giant Buddhas were blown up in 2001, and the Minaret of Jam (see: The Minaret of Djam, an Excursion in Afghanistan by Freya Stark). Meanwhile, UNESCO has put the cities of Herat, the city founded by Alexander as Alexandria Ariana, and Balkh, or, as it was called in antiquity Bactra or Zariaspa (see: Alexander’s Prison?) on a tentative list.
Although this is only a corner of our planet, there is more than enough to worry about!