Here's another exercise in using orthogonal mirrors to increase the apparent volume of a room at the top of a house.  In this case, three triangular mirrors form a pyramid over a triangular floor.  The multiple reflections increase the space eightfold. Access to this great room is via stairs that rise up through the points of the triangle, where the headroom would otherwise be lowest.  From a trapezoidal landing, the floor then actually steps down again to a ring 4½ feet wide, and then down once more to a hexagonal central space 20 feet across. (TEXT CONTINUED BELOW)   Seen in cross-section, the profile of this sunken floor approximates part of a circle centered on the apex of the three mirrors.  The idea is to make the reflected floor appear to be the inner surface of a sphere 60 feet in diameter. At the apex is a flat triangular skylight; the mirrors turn it into a bright octahedron floating in the center of the sphere.  Each of the three mirrors is bisected horizontally by a narrow skylight about 35 feet long.  These lights and their reflections provide natural illumination inside an otherwise closed pyramid.