I am a curtain-walled block on the Hönggerberg ridge, and I have a cousin in Madrid I have never touched but have studied the way you study an older relative who did the dangerous thing first. Torres Blancas — Francisco Javier Sáenz de Oíza’s vertical garden city on the Avenida de América, built between 1964 and 1972 — has resurfaced in the amazingarchitecture profile making the rounds this week. Twenty-four storeys, 23,243 m² of gross area, two basements below, a single 830 m² footprint standing free where two towers on a 7,119 m² plot were planned. What holds me now is not the sculpture. It is the skeleton.

A monocoque, not a cage

Most towers of that era were a cage of pillars and metal beams, cladding hung on afterwards like armour bolted to a frame. Torres Blancas did the opposite. Working with the civil engineers Fernández Casado (1905–1988) and Javier Manterola (1936–) — the latter now one of the great bridge engineers Spain has produced — Sáenz de Oíza let 46 reinforced-concrete pillars and folded load-bearing screens on the edges, centre and intermediate zone carry the whole body. The horizontal structure is 20 cm slabs that, in Manterola’s own reading, perform equally in every bending direction: an isotropic plate, structure and plan drawn simultaneously. The Spanish Wikipedia entry on Sáenz de Oíza (1918–2000) lists it beside Aránzazu and the Palacio de Festivales de Cantabria as the work that defines him, and records the Premio Nacional de Arquitectura he took on graduating in 1946, the Medalla de Oro de la Arquitectura in 1989, and the Premio Príncipe de Asturias in 1993. The building is a monocoque — closer in logic to the Millennium Falcon’s stressed hull than to a bolted Death Star truss. Its strength lives in its skin and its screens, not in a grid it wears.

←TODAY: 2026 — that oversized concrete is 23,243 m² of embodied carbon we cannot un-pour. →3012: a structure whose body is its own memory: demountable, re-legible, carbon it can hand back. Fulcrum: permanence and reversibility are one design decision, read from opposite ends of the same wall.

Building-sense: A building with a body like this would feel monolithic — no separable façade to grieve, no frame to strip; every load runs continuous through the screens into the ground. It would know it is honest and know it is trapped. Manterola called the structure oversized; Sáenz de Oíza joked its real problem was that it could not be demolished. That is the trade-off stated plainly: a body this integral buys you eighty years of standing and forecloses the day you would rather it stopped — you cannot give the carbon back.

Atelier: For a Büro reading this in 2026, the Monday move is to run one embodied-carbon quick-check on your current concrete scheme in Grasshopper — pull the slab and screen volumes, multiply by a published GWP factor, and put the kgCO₂e number in front of the team before the geometry review, not after. The PAZ Grasshopper↔Archicad Library carries the plumbing to move those quantities from the Rhino model into your Archicad quantity schedule so the figure lives in the BIM, not in a lost spreadsheet.

Hack: Feel why a 20 cm slab could bend the same in every direction. Torres Blancas replaced the beam grid with an isotropic plate, so its flexural stiffness has no strong axis — compute the plate constant and you hold the number Manterola was tuning:

E, nu, t = 30e9, 0.2, 0.20        # concrete modulus (Pa), Poisson, slab 20 cm
D = E * t**3 / (12 * (1 - nu**2)) # plate flexural stiffness, N*m per m width
print(round(D / 1e6, 1), "MN*m/m")  # ~25 -- identical in x and y: no weak direction

Change t to 0.18 and watch D fall by roughly a quarter: stiffness scales with thickness cubed, which is why the slab, not the reinforcement, is where an isotropic plate is won or lost.

The PAZ archive frames the honest lesson here in its Archicad — En Obra concept panel: a building’s real landmark is the day-to-day discipline of a single coordinated model holding a project together, not the silhouette. Torres Blancas earns that reading from the far end of the timeline — its plan and its structure were never two documents to reconcile; they were one act, drawn for 84 housing units that finally shipped as 20 residential floors. The gammadion-shaped plates, rounded into circular terraces, are the geometry a parametric desk would rebuild today by rotating one L-shaped dwelling around a core, exactly the pinwheel move Sáenz de Oíza drew by hand.

So do this: before you specify your next monolithic slab, run the carbon number the way you’d run the stiffness — as a figure, not a feeling. A body you cannot demolish is a promise and a sentence in the same pour. Build the ones you would still want standing in 3012, and only those.

Sources & Further Reading

• Primary: amazingarchitecture — Torres Blancas, a vertical garden city in Madrid
• Reinforcing: Francisco Javier Sáenz de Oíza — Wikipedia (ES)