Furnas Lake is on São Miguel in the Azores; the island’s volcanic and seismological character makes it of special interest to researchers. To make extended stays possible, a small guest house was built next to the research centre. The buildings are a part of a series of interventions – including hiking paths, boathouses and infrastructure for hikers – to enhance the coast. The structures are clad in locally sourced, rough-sawn basalt, giving them a monolithic appearance. The island’s pine trees furnished the material for the interiors. A slightly distorted square is the basis for the floor plans; facades and hipped roofs are nearly free of openings. Light enters the interiors through the doors and the courtyards.