Exceptional bit of post-post-industrial arrested-decay urban retro-medieval courtyard/house design for a mild climate that gets heat waves too: a double-layered brick wall on the ground floor of a residential building in a downtown San Francisco alley. Outer layer mock-crumbled away in a stylish scallop, inner layer a bit higher, both stopping short of the first-floor ceiling; the gap fenced with planks and rebar. Next to it, a tough fine-mesh steel security gate with extra steel lattice above.