There are currently 878 United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage sites around the globe. Of these 878 properties, 54 have been included on the World Heritage Committee's List of World Heritage in Danger. The list was compiled to inform the international community of conditions that threaten the existence of these notable sites.
Here are 11 UNESCO World Heritage sites that are currently in danger.
You probably know that Vienna is the capital of Austria, but did you know that the Historic Centre of Vienna is a UNESCO World Heritage site that's considered to be in danger?
According to UNESCO, the Historic Centre of Vienna developed from early Celtic and Roman settlements into a medieval and baroque city, the capital of the Austro-Hungarian Empire. As of 2017, Vienna's historic center has been on UNESCO's list of endangered properties due to a high-rise project that the organization says will undermine the area's value.
You may want to consider booking a trip to Vienna before construction of the high-rise begins. Before heading there, be sure to check out our list of eight things to see and do in Vienna .
Situated in the southern highlands of Bolivia, the City of Potosí was the world's largest industrial complex during the 16th century, according to UNESCO. The site comprises the industrial monuments of the Cerro Rico, an intricate system of aqueducts and artificial lakes that provide water to the community.
Since 2014, the City of Potosí has been on the list of World Heritage sites in danger due to continued and uncontrolled mining operations in the Cerro Rico that risk degrading the site.
Two former saltpeter refineries located in northern Chile, the Humberstone and Santa Laura Saltpeter Works, were declared UNESCO World Heritage sites in 2005. The refineries contain over 200 former saltpeter works where laborers from Chile, Peru, and Bolivia lived in company towns and forged a distinctive communal pampinos culture, according to UNESCO. Starting in the 1860s, Chile experienced a boom and became the largest supplier of natural saltpeter in the world.
Humberstone and Santa Laura Saltpeter Works were placed on the list of endangered sites because of the vulnerability of the structures and the impact of a damaging earthquake.
Located approximately 30 miles southwest of Alexandria, Abu Mena was a monastery complex, town, and Christian pilgrimage center in Late Antique Egypt. The entire complex, which consists of a church, baptistery, basilica, public buildings, streets, monasteries, houses, and workshops, was built over the tomb of the martyr St. Menas of Alexandria, who died in 296 A.D.
Abu Mena has been in danger since 2001 due to the water table rising as a result of a land-reclamation program for the agricultural development of the region. Moist soil has led to the collapse of many structures, and the risk of collapse for the rest of Abu Mena's ancient buildings is incredibly high.
The Tropical Rainforest Heritage of Sumatra in Indonesia is one of the most interesting and important rainforests on the planet, known especially for the long-term conservation of its distinctive and diverse biota, according to UNESCO.
Sumatra is home to an estimated 10,000 plant species, more than 200 mammal species, and around 580 bird species. Fifteen of the rainforest's mammal species, including the Sumatran orangutan, can only be found in this particular region of Indonesia.
The Tropical Rainforest Heritage of Sumatra is included on UNESCO's list for its number of endangered species. The Sumatran orangutan in particular is considered critically endangered by the International Union for the Conservation of Nature.
Considered a holy place by Jews, Christians, and Muslims, the Old City of Jerusalem has always been a place of great symbolic importance. According to UNESCO, the Old City of Jerusalem is recognized by all three religions as the site of Abraham's sacrifice. This small area constituted the entire city of Jerusalem until 1860, when the Jewish neighborhood of Mishkenot Sha'ananim was established.
The Old City of Jerusalem and its walls are considered to be in danger by UNESCO because of urban development, with construction around the Old City causing destruction and compromising the historical authenticity of its original buildings.
While the word Timbuktu -- particularly in the English language -- has come to mean any place that is very far away, the city is actually a UNESCO World Heritage site in Mali in West Africa. Timbuktu is home to the prestigious University of Sankore and other madrasas, or colleges for Islamic instruction.
According to UNESCO, Timbuktu was an intellectual and spiritual capital responsible for the propagation of Islam throughout Africa in the 15th and 16th centuries. Today, Timbuktu and its monuments are on UNESCO's list of endangered sites because, despite being continually restored, they are under threat from desertification.
Situated in Peru, the Chan Chan Archaeological Zone is a pre-Columbian city and archaeological site that was once the capital of the Chimu Kingdom. From 850 to 1470, before falling to the Incas, the Chimu Kingdom ruled the northern coast of Peru.
The Chan Chan Archaeological Site was the largest city of its kind in pre-Columbian America, and its extensive, hierarchically planned remains are impressive to behold.
Chan Chan is considered endangered because its ancient adobe structures are slowly turning to mud.
These four Serbian Orthodox Christian churches in Kosovo, a partially recognized state and disputed territory in Southeast Europe, are reflective of the high points of the Byzantine-Romanesque ecclesiastical culture, according to UNESCO. The monuments include the Decani Monastery, the Patriarchate of Pec Monastery, the Church of Holy Apostles, and the Church of the Holy Virgin of Ljevisa.
They are on UNESCO's endangered sites list due to the sheer age of the buildings and the conflict between Serbia and Kosovo. Kosovo attempted to gain independence from Serbia in 2008.
Liverpool, one of the world's major trading centers in the 18th and 19th centuries, played an important role in the growth of the British Empire. Six areas in the historic center and docklands of the city make up the UNESCO World Heritage site.
Liverpool became a major port for the mass movement of slaves and emigrants from Europe to America. It played a vital role in the development of modern dock technology, transport systems and port management, and building construction.
Today, the Maritime Mercantile City of Liverpool is considered to be in danger due to the proposed construction of Liverpool Waters, a massive redevelopment of the historic docklands north of the city center.
Everglades National Park is the largest tropical wilderness in the United States, the largest wilderness of any kind east of the Mississippi River, and the third largest national park in the nation.
Everglades National Park protects the southern 20 percent of the original Everglades in Florida. It became a UNESCO World Heritage site in 1979 for its water habitats that have become a sanctuary for large birds, reptiles, and various threatened species, including the manatee.
The park was placed on UNESCO's endangered places list in 1993 due to damage caused by Hurricane Andrew, and then it was removed from the list in 2007. It was placed on the list again in 2010 for issues of water flow reduction and nutrient pollution.