This document presents a taxonomy for developing critical spatial thinking skills through geospatial technologies. It was created as part of a PhD research project focusing on education for sustainable development. The taxonomy has two dimensions: 1) competencies of spatial citizens using geospatial technologies, and 2) critical spatial thinking skills and questions. It is based on frameworks for spatial thinking, critical thinking, education for sustainable development, and spatial citizenship. The taxonomy can help teachers design learning goals and educational strategies using geospatial technologies to enhance critical thinking in spatial thinking and support education for sustainable development.