Before the Sphere, the largest spherical building in the world (since 1989) was the Globe in Stockholm.
On it they sometimes project stuff on, which seems to be a way cheaper and energy efficient way than adding a billion LEDs.
Fun fact about the arena Globen, it’s actually the biggest piece in a art installation about our solar system, representing the sun. Pluto is about halfway up in Sweden.
It’s also the home arena of Swedens national ice hockey team.