Arnhildur Pálmadóttir was around three years old when she saw a red sky from her living room window. A volcano was erupting about 25 miles away from where she lived on the northeastern coast of Iceland. Though it posed no immediate threat, its ominous presence seeped into her subconscious, populating her dreams with streaks of light in the night sky.

Fifty years later, these “gloomy, strange dreams,” as Pálmadóttir now describes them, have led to a career as an architect with an extraordinary mission: to harness molten lava and build cities out of it.

Pálmadóttir today lives in Reykjavik, where she runs her own architecture studio, S.AP Arkitektar, and the Icelandic branch of the Danish architecture company Lendager, which specializes in reusing building materials.

The architect believes the lava that flows from a single eruption could yield enough building material to lay the foundations of an entire city. She has been researching this possibility for more than five years as part of a project she calls Lavaforming. Together with her son and colleague Arnar Skarphéðinsson, she has identified three potential techniques: drill straight into magma pockets and extract the lava; channel molten lava into pre-dug trenches that could form a city’s foundations; or 3D-print bricks from molten lava in a technique similar to the way objects can be printed out of molten glass.

Pálmadóttir and Skarphéðinsson first presented the concept during a talk at Reykjavik’s DesignMarch festival in 2022. This year they are producing a speculative film set in 2150, in an imaginary city called Eldborg. Their film, titled Lavaforming, follows the lives of Eldborg’s residents and looks back on how they learned to use molten lava as a building material. It will be presented at the Venice Biennale, a leading architecture festival, in May. 

Buildings and construction materials like concrete and steel currently contribute a staggering 37% of the worl...