Threatened by war: Ukraine's UNESCO World Heritage Sites

This 11th-century Eastern Orthodox church was built to rival the Hagia Sophia, in present-day Istanbul. Its mosaics and frescoes are prized for their impressive condition. The church greatly influenced subsequent temples, and together with the nearby monastic complex known as Kyiv-Pechersk Lavra, or Kyiv Monastery of the Caves, it helped the area become a center of Orthodox faith and thought.

With its dramatic mixing of styles, including Byzantine, Gothic and Baroque influences, this former residence of the Eastern Orthodox metropolitan bishop expresses the diverse religious and cultural identity of the Austro-Hungarian empire. Built by Czech architect Josef Hlavka from 1864-1882, the giant complex also includes a chapel, seminary and a monastery.

Founded in the late Middle Ages, the western city of Lviv was an important center of administration, religion and commerce for centuries. The modern city still bears its medieval hallmarks, including places of worship for various religious communities. It also boasts many Baroque buildings. Its architecture shows how Eastern European influences mixed with ones from Italy and Germany.

The Struve Arc is a chain of survey triangulations spanning more than 2,820 kilometers and 10 countries. Its southernmost point is in the Ukrainian town of Staro-Nekrasovka, on the Black Sea, while its northernmost point is in Hammerfest, Norway (above, in 1895; no photo from Ukraine available). Built from 1816-55, the collaborative structure helped determine Earth's exact shape and size.

The ruins of Tauric Chersonese, a 5th-century BC city founded by the Dorian Greeks, are located outside of Sevastopol, in southwest Crimea, which was illegally annexed by Russia in 2014. The site includes public building complexes, residential neighborhoods and early Christian monuments, well-preserved vineyard parcels and related systems, as well as remnants of Stone and Bronze age structures.

This UNESCO World Heritage Site is actually a series of 16 "tserkvas," or churches, that are spread out over Poland and Ukraine in the mountainous Carpathian region. The wooden log structures were built between the 16th and 19th centuries by both Orthodox and Greek Catholic communities. They exemplify the timber-building tradition of Slavic countries, and their interiors are also quite renowned.

Also located in western Ukraine is the natural World Heritage Site of ancient and primeval beech forests. The site in its entirety includes 94 areas in 18 countries. This photo is of the Uholka-Shyroki Luh forest, which is part of the world's largest primeval beech forest. Beech started spreading after the last Ice Age, 11,000 years ago, and are now part of pristine, complex ecological systems.