The British Museum has just finished a huge, £135 million ($231 million) expansion, but virtually nobody knows about it. That’s because the expansive new facility, which was designed by the firm of star architect Richard Rogers, is completely tucked into the gap between the sprawling institution’s older buildings, and buried beneath its floors. It was designed for back-of-house purposes—including storage facilities the size of 14 Olympic pools and a 42-ton truck lift dubbed Europe’s largest—which have never before been so integrated at the museum, the Guardian reports.

Dubbed the World Conservation and Exhibitions Centre (WCEC), the new facility centralizes the institution’s conservation efforts and collections activities in a set of four sunken pavilions—a full 70 percent of the WCEC is located below ground. Above ground, the inconspicuous modernist addition houses modular conservation studios and labs flooded with natural light that can be reconfigured to accommodate the incredible variety of artifacts with which the museum deals.

“It’s a nice change from our Georgian servants’ basement,” Pippa Pearce, the museum’s senior conservation officer, told the Guardian. “Before, we were on top of each other and looking up at the outside world through bars, but now we’re in this wonderful light and airy space. We finally have the world-class facilities to work on our world-class collection.

The WCEC also boasts a green roof, which will eventually feature plants, nesting boxes for birds, and beehives that will house a colony of honey bees—resulting, we hope, in British Museum honey, not unlike that harvested and sold by the Whitney Museum.

The construction of the new facility was the subject of a project by artist-in-residence Liam O’Connor, whose work was on public display in the WCEC Model room last month.