Lisbon.

Affordable, dense, and climate-aware: a generation of architects in Lisbon is taking on the contradiction at the heart of European housing, and the city is, gingerly, helping them.

On a narrow street in Arroios, a four-storey building waits for a decision. Its facade is dressed in blue-and-white azulejos — the glazed ceramic tiles that have skinned Lisbon's buildings for the better part of two c…