The Las Vegas skyline has been dominated by a huge animated dome – billed as the world’s largest video screen – dwarfing surrounding high-rise hotels after going live with a 300ft eyeball looking down over the city.

The MSG Sphere’s 580,000 sq ft fully programmable LED screen, named the Exosphere, was illuminated for pre-launch testing overnight to celebrate the Fourth of July. The show started with a welcome message, “Hello world”, followed by fireworks and stars and stripes animations, a moon in a night sky and an imposing Halloween pumpkin. Videos showed the screen overshadowing cars – tiny in comparison – on a nearby road.

A similar project has been proposed for east London but has hit significant delays.

Built to host concert events, the Las Vegas structure will have capacity for tens of thousands of people and is reported to have cost $2bn (£1.6bn) to construct. It has been built by Sphere Entertainment Co in partnership with the sports powerhouse Madison Square Garden Entertainment.

“The Exosphere is more than a screen or a billboard – it is living architecture and unlike anything that exists anywhere in the world,” said Guy Barnett, senior vice-president of brand strategy and creative development at MSG Sphere.

The exterior consists of approximately 1.2m LED “pucks”, each containing 48 individual LED diodes capable of displaying 256m different colours.

The Sphere will open officially on 29 September with U2: UV Achtung Baby Live at Sphere.