What does architecture look like when its designers are free to explore the limits of their imaginations, creating structures that are more like monumental sculptures than conventional buildings? The “Solo Houses” project in Matarraña, Spain, creates a space where such ideas can become realities in the form of holiday homes, all 12 of which have been designed by budding international architecture practices across a hilly 99-acre property. Dreamed up by French developer Christian Bourdais and first announced in 2010, the project takes inspiration from previous experimental architecture programs meant to spark innovation.

Inverted Pyramid Solo House - TNA

The recently unveiled “Inverted Pyramid Solo House” by Tokyo-based firm TNA, led by Makoto Takei and Chie Nabeshima, evades all expectations of conformity with its monolithic and seemingly precarious silhouette. Currently under construction at the Matarraña site (along with the rest of the houses), this upside-down pyramid almost seems to have fallen from the sky, wedging itself just deep enough into the soil to avoid falling over.

Inverted Pyramid Solo House - TNA

The home’s seemingly impenetrable exterior is pierced only by a few trapezoidal cutouts, which allow natural light and fresh air inside via sliding glass panels. Its wide open interior is divided by platforms at various levels, all of them projecting from exterior walls and elevating private spaces like the home’s three bedrooms far above the common ones without cutting them off from the rest of the structure.

Inverted Pyramid Solo House - Interior

Guests enter through the home’s intermediate level from the high end of the slope, and one of the cut-outs offers access to the landscape at the lower end. Initial renderings even illustrated a pyramid-shaped swimming pool set just down the hill, with an oversized diving board-inspired platform providing a fun way to jump right into it. Unfortunately, this feature seems to have been nixed from the final design.

Even without this secondary volume, the home is striking, highly sculptural, and visually complementary to the spare, dry landscape around it. Nonetheless, the rooftop feels a bit like a missed opportunity. It would be tempting to climb up there to take advantage of that broad flat surface and gaze out at the terrain.

Solo Pezo - Pezo von Ellrichshausen Architects

The first Solo House to actually be constructed was “Solo Pezo” (pictured above), a project by Chilean practice Pezo von Ellrichshausen Architects. This monolithic concrete structure rests on a square platform, elevated above its surroundings, with a deep swimming pool set into its center. The second was “Solo House II” (below), a beautiful ring-shaped home on a forested hilltop by Office KGDVS.

Solo House II - Office KGDVS

Other participating architecture firms include Sou Fujimoto, Johnston Mark Lee, Studio Mumbai, MOS Office, and Didier Faustino’s Mésarchitecture. These firms are all known for pushing boundaries, often showing off their more experimental ideas in the form of temporary pavilions.

Inverted Pyramid Solo House - Interior Inverted Pyramid Solo House - Interior

“An interesting point is how these architects read society and how they integrate this reading into their buildings,” says Bourdais. “It has a strong sociological interest. Each project of the Solo Houses collection is one very different reading of society.”

Once complete, the Solo Houses will be available to the public as vacation rentals. Casa Pezo, which sleeps five, is already listed on the Boutique Homes booking site with a fairly open calendar and rates starting around $540 USD per night.