Iranian-French architect India Mahdavi has put her characteristic maximalist spin on PoMo, a contemporary art museum in Trondheim, Norway, with a salmon-pink gift shop and a mandarin-hued staircase.

PoMo, which opened its fuchsia doors on Saturday 15 February, is housed within Trondheim's Grade I-listed Art Nouveau Post Office building originally constructed in 1911.

Known for her use of bold colour and shape, Paris-based Mahdavi collaborated with Norwegian architect Erik Langdalen to renovate the site and transform it into a five-storey modern and contemporary art museum spanning 4,000 square metres.

The pair sought to balance the building's history with references to Trondheim's skyline and Norwegian folk art and craftsmanship.

Visitors enter via the hot-pink metal and glass entrance, which contrasts with the otherwise untouched brick-clad facade. Arched rainbow signage reading "our magic hour" was erected on the roof of the museum, acting as a vibrant beacon and landmark.

Inside, three gallery spaces feature on floors one, two and three, while the basement is reserved for special projects and the fourth floor is a dedicated private lounge.

"We orchestrated the spaces of the building through the prism of hospitality," Mahdavi told Dezeen.

"The museum is different from a restaurant and different from a hotel, but features both the experiences of sharing and intimacy," she continued. "It was about creating a sense of permeability and a place where visitors can feel welcome."

The designer explained that the interior is interspersed with distinctive "in-between spaces". These include the all-pink gift shop that is finished with floor-to-ceiling ash cabinetry.

"The shop is a chromatic reference to the famous Norwegian salmon," said Mahdavi.

Langdalen designed a meandering back-lit steel staircase in a mandarin-orange hue, informed by the colour of the many warehouses located on the nearby Nidelva river.

"My first invitation to design a museum was an opportunity to widen the spectrum of my signature style of using colour and wonder," explained Mahdavi.

A gabled reading room on the third floor was created in Mahdavi's trademark style, complete with a pixelated green carpet and decorative murals depicting oversized sea creatures, alphabets and flying books designed with Dutch "ornamental modernism" studio Freeling Waters.

"The space draws inspiration from a forgotten Nordic folkloric art – its codes are renewed to create a pop version of folklore," said Mahdavi.

PoMo will host two major exhibitions per year as well as a permanent collection, which has dedicated a minimum of 60 per cent of its acquisitions budget to women artists.

"At the moment, we are already approaching 40 per cent of women artists in the PoMo collection," said museum director Marit Album Kvernmo. "The collection consists of works across media, including sculptures, installations and paintings."

PoMo currently includes pieces by late leading artists such as Louise Bourgeois, Franz West and Sol LeWitt as well as the work of emerging artists.

"It's always exciting to address new subjects in new countries," reflected Mahdavi, considering the experience of designing her first museum.

"It's also the first time I have worked in Norway – I'm very grateful to have had this unique opportunity as an interior designer to have been able to express my vision of joy," she added.

"For the past two years, I have felt like a lucky conductor directing an orchestra of talents, from artisans to workers and artists."

Mahdavi's portfolio, which spans architecture and design, also includes the decadent remodelling of the Gallery dining room at London restaurant Sketch and the renovation of six rooms within Rome's 16th-century Villa Medici.

The photography is by Valérie Sadoun.