A sky lantern, also known as Kongming lantern or Chinese lantern, is a small hot air balloon made of paper, with an opening at the bottom where a small fire is suspended. In ancient China, sky lanterns were strategically used in wars for military communication (transmitting secret messages) or lighting the sky when laying siege on the city at night. Later they were incorporated into festivals like the Chinese Mid-Autumn and Lantern Festivals. Thanks again Rodrigo!