Some of these wonders are part of the Global Heritage Fund's first annual list of five endangered cultural sites, issued to mark the day and draw attention to the fund's work. The day was first adopted as a concept in 1983 to draw attention to the cultural heritage of communities around the world.
Sites include a natural Guatemalan wonderland larger than Yellowstone National Park, Colombia's Lost City and medieval villages in the Transylvanian Alps.
The fund, which works to protect significant and endangered cultural heritage sites in the developing world, named sites they're working to save from the impact of uncontrolled modern development, tourism and looting.
"Many cultural sites are endangered, especially those in the developing world (regions where per capita income is less than $2 per day), and they languish without any international attention," wrote Vince Michael, the fund's executive director, via e-mail. "It's our hope that World Heritage Day and our list will inspire community involvement in preserving the legacy of these sites."
Why focus on these five sites?
Some locations were chosen for their historical significance.
"Ciudad Perdida (in Colombia) was once a thriving center of political, social and economic power, and Göbekli Tepe (in Turkey) is the oldest man-made place of worship discovered to date. As awareness of these two sites has grown, threats such as unregulated tourism and looting could harm the sites," Michael wrote.
The Minority Villages of Guizhou (in China) and the Carpathian Villages (in Romania) were included because of their important cultural heritage and traditional practices, "which are being eroded by modern development and industrialization," Michael said.
"Finally, we included Mirador, Guatemala, because it is facing critical environmental threats -- ranching and logging have destroyed 70 percent of its forests in the last decade."