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Liverpool Maritime Mercantile City, UK - Significance: Its six areas in Liverpool's historic center and docklands played an important role in developing one of the world’s major trading centers in the 18th and 19th centuries.

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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.

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Historic Centre of Shakhrisyabz, Uzbekistan -

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

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Historic Centre of Shakhrisyabz, Uzbekistan -

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

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Ancient City of Aleppo, Syria - Significance: Situated at the crossroads of different trade routes of the 2nd millennium BCE, Aleppo has witnessed the rise and fall of a handful of empires and civilizations, including the Hittites, the Assyrians, the Arabs, the Mongols, and the Ottomans.

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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.

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Medieval Monuments in Kosovo - Significance: The site's four main buildings reflect the height of the Byzantine-Romanesque ecclesiastical culture.

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Medieval Monuments in 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.

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Chan Chan Archaeological Zone, Peru - Significance: As the capital of the Kingdom of Chimor, Chan Chan, a large adobe city in the Moche Valley of what is now Trujillo, reached its peak in the 15th century and became the largest city of pre-Columbian South America.

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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.

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Archaeological Site of Cyrene, Libya - Significance: Cyrene, established by the Greeks of the island of Thera (present-day Santorini), was a major city of the Hellenic world. It was later taken by the Romans, who continued to develop it until the earthquakes of 262 and 365 CE when it was deserted, according to the Ancient History Encyclopedia.

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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.

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Old City of Jerusalem and its Walls, Jerusalem - Significance: Considered a holy site by all three Abrahamic religions, Jerusalem's cultural significance is immense. For example, the site of the Dome of the Rock, a seventh-century Islamic shrine, is recognized by the three faiths as the place of Abraham's sacrifice.

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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.

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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.

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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.

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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.

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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.

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Historic Center of Vienna, Austria - Significance: Austria's capital city evolved from early Celtic and Roman settlements into a medieval and Baroque city and culminated in the capital of the Austro-Hungarian Empire, during which it established itself as the leading European music center.

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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.

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Potosí, Bolivia - Significance: Perched 4,000 m above sea level, Potosí was considered the world’s largest industrial complex in the 16th century as a result of its silver mines.

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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.

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Abu Mena, Egypt -

Significance: The holy city, monastery complex, and Christian pilgrimage hub was built over the tomb of the martyr Menas of Alexandria, who died in the late third century.

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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. 

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Tomb of Askia, Mali -

Significance: Built in 1495, this 17-meter pyramidal structure is believed to be the burial site of Askia Mohammad I (sometimes spelled Muhammad or Mohamed), a prolific emperor of the Songhai Empire.

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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. 

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Portobelo-San Lorenzo, Panama - Significance: The fortifications on the Caribbean Side of Panama: Portobelo-San Lorenzo were built in the 17th and 18th century by the Spanish Crown to protect transatlantic trade.

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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.

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

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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.

See also: Where to find America’s most compelling UNESCO World Heritage Sites

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