BARCELONA, Spain — Drivers circling Barcelona’s Plaça de Francesc Macià might not realize the architectural significance of the unusual curved building that overlooks this busy intersection.

At 11 floors from ground level, it is dwarfed by the surrounding office and apartment blocks, but the innovative concept of the 1960s-designed edifice means it has architectural stature. Protected as a historic monument by the Spanish government, Francesc Macià 10, as the building is known, is being transformed from out-of-date offices into eight luxury residences.

“When we saw Francesc Macià 10 in 2012, we were aware it was a great opportunity,” said José Caireta, managing partner of Squircle Capital, a Spanish development firm. “The location of the building is unique and it was perfect for a commercial mixed-use and residential project.”

The original design of Francesc Macià 10 was created by Marc-Joseph Saugey, a Swiss architect whose work gained prominence in the 1950s. It was commissioned by the Swiss insurance firm Winterthur and in its early days was criticized for its distinctly modern style.