The NATO Star Sculpture: History and Symbolism (nato.int)

• The NATO star was installed in 1971 at the original Brussels headquarters.
• It is made of factory-oxidized steel and weighs 6 metric tonnes.
• It was moved to the new NATO HQ in May 2016.

"The NATO star sculpture, designed by Belgian architect Raymond Huyberechts, was installed at NATO's Brussels headquarters in 1971. Originally budgeted at 1.5 million Belgian francs, the 7-meter-high, 6-tonne steel structure symbolizes the Atlantic alliance. It was moved to the new headquarters in 2016, and featured on Belgian postage stamps for NATO anniversaries."