Today we are celebrating the heritage and culture of Indigenous populations worldwide. There are some 5,000 Indigenous cultures in 90 countries around the world, from Samoa and Greenland to New Zealand and Nepal. One of the major challenges they face is the loss of their languages: It's estimated that of the 4,000 Indigenous languages in the world, around 2,600 are in danger of becoming extinct.

In the city of Cusco, Peru, the stone walls of Sacsayhuamán, seen in today's image, murmur tales of the mighty Inca civilization. The citadel's walls, which extended over 1,000 feet, were built in the 15th century. The boulders used to make them were carved and placed without mortar. After the Inca Empire was defeated in a battle here in 1536, Sacsayhuamán was dismantled by the Spanish. The rest of the structure was covered in earth until 1934, when it was rediscovered during an excavation. Today is a good day to discover more about Indigenous peoples, and the importance of preserving their cultures for future generations.