It is a suitably truculent metaphor for this forthright city, which in 2016 turned down the prospect of having its own Guggenheim Museum, after five years of bitterly contested public debates. While the Guggenheim’s mooted harbour-front location remains empty (earmarked as a potential site for a new architecture and design museum, announced last week), the opening of the privately funded Amos Rex adds convincing weight to the argument that Helsinki is a world-class cultural destination in its own right, without the need for a branch of the US franchise.

Beneath the lumpy landscape stretches a gargantuan 2,200 sq m flexible exhibition space (almost twice the size of the V&A’s new underground gallery), which has been cleverly excavated in the centre of town, between a former army barracks and the Lasipalatsi, or glass palace, a 1930s entertainment and retail complex. This glory of Finnish functionalism has been immaculately restored, with timewarp interiors of fleshy salmon columns, a sweeping spiral staircase and spherical glass light fittings that dangle like clumps of frogspawn from bright red and blue ceilings. Its 500-seat cinema is a wonder of the period, with chrome-edged red upholstered seats, flying saucer lamps and pleated mustard-coloured curtains. Outside, the building’s former boilerhouse chimney stands proudly in the centre of the new square with a nautical air, like the funnel of a ship now cast adrift in the churning sea of paved mounds.

After all this digital wizardry, the small room dedicated to a permanent exhibition of post-impressionist paintings seems like an afterthought, tucked into a low-ceilinged windowless space – something the architects had to include but didn’t quite know how.

The large column-free hangar has become the default desire for most new museum extensions – but it so often ends up being compartmentalised and blacked out. It will be interesting to see how Amos Rex’s next two exhibitions, spanning the diverse poles of surrealist painter René Magritte and experimental Dutch art collective Studio Drift, make use of the great concrete tent.

Up above, more families are clambering on the mounds and peering in through the windows to get a glimpse inside their new cultural bunker. The architects hope their sloping landscape will become a spontaneous auditorium for outdoor concerts and events, but even without any performances it has already become a magnet of activity in the middle of the city, whose oversized squares often feel a bit windswept. And there’s a spectacular gallery underneath it, to boot.