Lisbon has just inaugurated its new MAAT (Architecture, Art and Technology) museum complex with a new building by London-based AL_A. An exercise both in sculptural expressiveness and contextual restraint, the structure’s low-slung form has been designed to keep views from the streetscape behind it unobstructed, while its resolutely organic and fluid form contrasts powerfully with the existing rectilinear and recently refurbished Central Tejo power station next door.

The 190m-long building alluringly unfolds and reveals itself as visitors make the journey around and on top of its gently undulating form and through its flowing interior spaces. Its arched façade is adorned with 15,000 three-dimensional off-white (but slightly speckled and crackled up-close) geometric tiles that were chosen for the way they reflect and interact with the southern light and the shimmering Tagus river below, says Maximiliano Arrocet, a director at AL_A and project architect for the building. 'The first time we came here was in November and the whole site was bathed and tinted in a golden orange and yellow light,' he recalls. 'We were blown away and realised the river had to be a critical part of how we thought about the building.'

Inside, the four main spaces are separate but connected in one fluid, almost aquatic, downward journey. The Main Gallery features a dramatic skylight with reflective steel fins that provides views in and out, and fascinating glimpses of the tiles and shifting light above; while the largest – which will be free for visitors year round – is an ellipse with a spiralling ramp staircase around it, that is currently hosting a multi-layered sound, light and performance piece by French artist Dominique Gonzalez-Foerster.

Though the contemporary art space officially opens today, its real completion will be in mid-2017, when the surrounding landscape by Vladimir Djurovic is planted and, above all, a 60m pedestrian bridge (also by AL_A) is installed, connecting the publicly accessible roof with the neighbourhood of Belém behind it. 'The bridge is a fundamental part of the project,' explains Arrocet, 'because the people across the railway and highway will finally be connected to the water.'

In the meantime the roof, with its elegantly tapered lines and alternately stepped and smooth slopes, is already fully accessible (for wheelchair users too) and the view out to the estuary and the striking Padrão dos Descobrimentos (Discoveries Monument) is unobstructed and memorable. But perhaps more importantly, 'you can also turn your back on the river and see the city as you have never seen it before', says Amanda Levete, principal at AL_A. 'The connection between river and city is literal as well as metaphysical.'