While the homeowners' choice to build their new ultra-insulated passive house on an urban infill lot made sense on many levels, it also led to some major challenges. A massive basalt outcrop dominated the site, resulting in the lot remaining vacant for decades as the neighborhood grew around it. The architect sited the home on top of the outcrop with retaining walls around the home to create a flat plane to build on. Even pushing the limits this way resulted in limited outdoor space, but the intimate courtyard areas provide make the most of what's available. To construct the retaining walls, a base course of basalt boulders was anchored into the existing outcrop, with the walls built up from there. The structural retaining wall is topped by another level that acts as a barrier to the steep drop.