This study aims to explore mathematical concepts contained in the Nawang Pajo Gendang house in West Manggarai which can be used as a medium for learning mathematics, especially geometry. This research is qualitative descriptive research with an ethnographic approach. Based on the results of observations, several mathematical concepts were obtained in the House of Gendang Nawang Pajo West Manggarai. The results showed that the parts of the Nawang Pajo Gendang house in West Manggarai related to mathematical concepts include carvings on the end of the rooftop of the Gendang house, the rooftop of the Gendang house, and the model and shape of the Gendang house are closely related to the concept of Geometry including building flat and building space and transforming geometry including dilatation and reflection.