This is the Friendship of Nations Arch in Kyiv, the capital of Ukraine. It was erected in 1982 during the Soviet era to celebrate the country’s unification with Russia.
Eurovision 2021
BuzzFeed: A Soviet monument got a rainbow makeover and people have opinions
Kyiv workers attach colored paper to the Arch of Friendship in Mariyinsky Park in Kyiv, transforming it in the “Arch of Diversity” to fit this year’s Eurovision Song Contest theme to “Celebrate Diversity.”