World Heritage Sites that could disappear anytime

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Medieval Monuments in Kosovo

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

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.

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.

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.

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.

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.

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.

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.

Coro, Venezuela

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