© Getty Images

Archaeological Site of Cyrene, Libya -

Significance: Cyrene was an important city in the Hellenic world. It was established by the Greeks of the island of Thera (present day Santorini). The city was later taken by the Romans, who developed it until it was hit by earthquakes in 262 and 365 CE before being abandoned, according to Ancient History Encyclopedia.

© Shutterstock

Archaeological Site of Cyrene, Libya -

Why it's endangered: UNESCO added the city—as well as five other Libyan sites—to its List of World Heritage in Danger in 2016, following damage caused by unrest in the country, according to the The Libya Observer.

© Shutterstock

Medieval Monuments, Kosovo -

Significance: The site's four main buildings showcase the height of Byzantine-Romanesque ecclesiastical culture.

© Shutterstock

Medieval Monuments, Kosovo -

Why it's endangered: UNESCO added these monuments to its list of World Heritage in Danger in 2006 due to a rise in the region's political instability, which rendered the site's management and conservation difficult.

© Shutterstock

Liverpool Maritime Mercantile City, UK -

Significance: The six areas in Liverpool's historic center and docklands were crucial to the development of a major global trading hub in the 18th and 19th centuries.

© Shutterstock

Liverpool Maritime Mercantile City, UK -

Why it's endangered: UNESCO placed it on the List of World Heritage in Danger in 2012 following a proposal to build a massive redevelopment of the historic docklands.

© Shutterstock

Humberstone and Santa Laura Saltpeter Works, Chile -

Significance: The two former saltpeter refineries in the remote Pampas of northern Chile served as a community for thousands of workers throughout the first half of the 20th century, until they became ghost towns in the 1950s.

© Shutterstock

Humberstone and Santa Laura Saltpeter Works, Chile -

Why it's endangered: UNESCO added the ghost towns to its List of World Heritage in Danger in 2005 when the Tarapacá earthquake caused significant damage to the site.

© Shutterstock

Historic Centre of Shakhrisyabz, Uzbekistan -

Significance: Located on the the ancient Silk Road in southern Uzbekistan, this historic center dates back 2,000 years. It served as the cultural and political hub of the Kesh region, in the 14th and 15th century.

© Getty Images

Historic Centre of Shakhrisyabz, Uzbekistan -

Why it's endangered: UNESCO added it to the list of World Heritage in Danger in 2016 due to the development of tourist infrastructures that propose the demolition of historic sites and buildings.

© Getty Images

Ancient City of Aleppo, Syria -

Significance: Aleppo, located at the intersection of various trade routes of the 2nd millennium BCE, has been a witness to the rise and fall of a handful of empires and civilizations. These include the Hittites, Assyrians, Arabs, Mongols, and Ottomans.

© Shutterstock

Ancient City of Aleppo, Syria -

Why it's endangered: UNESCO added Aleppo—as well as six other Syrian cities—to its list of World Heritage in Danger in 2013 after escalation of the country's armed conflict.

© Shutterstock

Chan Chan Archaeological Zone, Peru -

Significance: Chan Chan, capital of the Kingdom of Chimor, was located in the Moche Valley (currently Trujillo). It emerged as the largest city of pre-Columbian South America, peaking in the 15th century.

© Shutterstock

Chan Chan Archaeological Zone, Peru -

Why it's endangered: UNESCO added Chan Chan to its list of World Heritage in Danger in 1986, the same year it was designated as a World Heritage Site. Chan Chan is threatened by illegal farming practices, legal land ownership and relocation issues, as well as urban and infrastructure overdevelopment.

© Shutterstock

Old City of Jerusalem and its Walls, Jerusalem -

Significance: Jerusalem holds great cultural importance as a sacred site for the three Abrahamic religions. The Dome of the Rock, a historic Islamic shrine built in the seventh century, is revered by all three faiths as the place where Abraham's sacrifice occurred.

© Shutterstock

Old City of Jerusalem and its Walls, Jerusalem -

Why it's endangered: UNESCO added Jerusalem to its List of World Heritage in Danger in 1982 amid controversy, as stated on its website. Jerusalem is at risk due to destruction of religious properties, urban development plans, lack of maintenance and responsible management, among other reasons.

© Shutterstock

Samarra Archaeological City, Iraq -

Significance: Throughout the 9th century, this former powerful Islamic capital city ruled over the provinces of the Abbasid Empire, which extended from Tunisia to Central Asia.

© Getty Images

Samarra Archaeological City, Iraq -

Why it's endangered: UNESCO added Samarra to its List of World Heritage in Danger in 2007, the same year it was designated as a cultural heritage. The main threats to the site arise from a lack of proper management by local authorities, according to UNESCO.

© Getty Images

Historic Center of Vienna, Austria -

Austria's capital, Vienna, has a rich history. It has evolved from early Celtic and Roman settlements, into a medieval and Baroque city, to become the capital of the Austro-Hungarian Empire. During this time, Vienna became a major music center in Europe.

© Shutterstock

Historic Center of Vienna, Austria -

Why it's endangered: UNESCO added Vienna's historic center to its List of World Heritage in Danger in 2007 in light of a proposed high-rise project that could negatively impact it, according to The Guardian.

© Shutterstock

Potosí, Bolivia -

Significance: Potosí, perched 4,000 m above sea level, was renowned in the 16th century for its silver mines, making it the world's biggest industrial complex.

© Shutterstock

Potosí, Bolivia -

Why it's endangered: UNESCO added the site to its List of World Heritage in Danger in 2014 due to degradation of the Cerro de Potosí, caused by continuing mining operations.

© Shutterstock

Abu Mena, Egypt -

Significance: The importance of this place lies in its status as a sacred city, as well as a monastery complex and a site of pilgrimage for Christians. It was constructed on top of the tomb of the martyr Menas of Alexandria, who passed away in the late third century.

© Getty Images

Abu Mena, Egypt -

Why it's endangered: UNESCO added the archaeological site to the List of World Heritage in Danger in 2001 following agricultural efforts in the area that led to a considerable increase in water levels in the soil, causing several other structures to collapse. 

© Getty Images

Tomb of Askia, Mali -

Significance: Constructed in 1495, this 17-meter pyramid-like construction is reputedly the resting place of Askia Mohammad I, a prolific emperor of the Songhai Empire.

© Getty Images

Tomb of Askia, Mali -

Why it's endangered: UNESCO placed the tomb on its List of World Heritage in Danger in 2012 in an effort to mitigate the threats caused by the armed conflict in the region. 

© Getty Images

Portobelo-San Lorenzo, Panama -

Significance: The fortifications on the Caribbean side of Panama, known as Portobelo-San Lorenzo, were constructed in the 17th and 18th century by the Spanish Crown. These fortresses played a vital role in safeguarding transatlantic trade.

© Shutterstock

Portobelo-San Lorenzo, Panama -

Why it's endangered: UNESCO added the fortifications to its List of World Heritage in Danger in 2012 due to environmental factors, lack of maintenance, and urban developments.

© Shutterstock

Coro, Venezuela -

Significance: Dating back to 1527, this city is unique for its fusion of local traditions, Spanish Mudéjar, Antillean, and Dutch architectural styles.

© Shutterstock

Coro, Venezuela -

Why it's endangered: UNESCO added the port city to its List of World Heritage in Danger in 2005 following two consecutive years of heavy rains that considerably damaged several buildings, according to the Smithsonian.

© Shutterstock