Palmyra is an ancient Semitic city that grew wealthy through its location at the Silk Route. The wealth enabled the city to realize monumental building projects like the Great Colonnades, the Temple of Bel, or the tower tombs. Throughout the centuries Palmyra belonged to many empires, the people prayed to many gods, and it absorbed many cultures. The mix lead to distinctive art and architecture typical for just this one place on earth. Thus it was named an UNESCO World Heritage site. During the Syrian Civil War it first came to looting and damage do to the fighting. Then ISIS started to demolish the sites in an act of modern iconoclastic fury.
(Note: Palmyra was also the location of one of the most horrible prisons of the Assad regime in Syria: Tadmor Prison. I want to mention it because it should not be forgotten either. But I don’t think the presence of one justified the destruction of the other. And while the prison walls might be gone now the horror and oppression the prison has seen clouds now the whole area without any limits.)