As of 2019, one out of four UNESCO World Heritage Sites is under threat by climate change, each with few protections against their respective worst case scenarios. Increased humidity, rising sea levels and other climatological factors are newly placing increased pressure of century and millennia-old structures that have been the symbols of permanence throughout known history. Here are a few that fall under such threats:

1. Piazza San Marco. Venice, Italy

Spread out over 118 islands, Venice as a city has knowingly been under threat by rising sea levels and land subsidence for several years. However, its Piazza San Marco, one of the oldest and most prized plazas in all of Europe, is in an especially precarious position - just steps from the island's edges.

2. Rapa Nui (Easter Island)

The Chilean Island of Rapa Nui, world famous for its mysterious Moai monoliths buried half-way across its landscape, is currently being eroded by increasing sea levels and higher-than-average waves.

3. Thu Bon River. Hoi An, Vietnam

Though much of the city of Hoi An is two meters or less above sea level, its historic old town of over 800 wooden-framed buildings from the 16th and 17th centuries are presented with climatological threats unseen in previous centuries.

4. Mount Everest. Sagarmatha National Park, Nepal

The famed mountain of Nepal's Sagarmatha National Park has been seeing increasingly raised temperatures in the last several decades, which has caused glaciers in the ridge to melt and otherwise retreat. This will make traversing the mountain increasingly difficult for hikers and native animals alike.

5. Sultan Ahmed Mosque. Istanbul, Turkey

First constructed in 1616, Sultan Ahmed Mosque has seen many renovations in its 400-year history. However, it is newly threatened by increasing temperatures and sea level rise that can negatively effect its base level and material palette.