In 1979, the United Nations declared the International Year of the Child. It was in the city of Sofia that the first international children's assembly was organized in which children from 79 countries participated. On this occasion, a memorial is also built, known nowadays as "The Bells" and featuring 69 bells from different countries (which can only be rung by children). The motto of the project is "Unity, creativity and beauty". There are claims that the name and main motto were borrowed from the philosophical system of Nicholas Roerich (a Russian artist and philosopher). The assembly is held every three years, with a record attendance of 138 countries in 1988. In 1990, the overseas structures of "Peace Banner" were closed.
After 1999, attempts were made to revive the initiative, but on a much smaller scale and success rate. Anyone who wishes can visit the memorial and admire the bells, which are distinguished by their nationality and uniqueness. The location of the complex is near the Vitosha mountain on the outskirts of the city of Sofia.