Located less than an hour away from Mexico City, Tepoztlan's Tubohotel is an affordable hotel that uses recycled concrete tubing for its rooms. Each tube is equipped with a queen-sized bed, with glass side that overlooks a beautiful panoramic view of the area. I know, I know. Concrete is not the most sustainable building material, but this hotel uses recycled concrete tubing for its rooms, with each room stacked in pyramids of threes.
(images: via Treehugger)