Mountain Shadows Montessori was one of Haertling's last projects, and one that he had interest for. A triangular floor plan with an inward sloping roofline incorporates an enclosed playground area. Economy was a concern, so the building was set in the ground for insulation. This is taken up by the architect as a design concept, as with the Quaker Meeting House, for the exterior rounded-edge windows and graded landscaping. This is also one of the many ways that the building would be a delight for children.