Researchers have created a 3D printing robot that uses organic materials to build some truly stunning sandcastles. The Stone Spray project, created by Anna Kulik, Inder Shergill, and Petr Novikov at the Institute for Advanced Architecture of Catalonia, was intended to explore a new way of creating architecture out of soil. The robot uses a jet spray system to deliver a mixture of soil — or sand, in the video below — and an eco-friendly liquid binder to a surface, building solid architectures that don’t crumble when the wind picks up. Fitting with the project’s aims to remain environmentally friendly, the robot uses very little energy and can run entirely on solar power. To see it in action, check out the video below.