This week Dallas is celebrating its newest landmark, a goodie but not an oldie.

The Landmark Commission voted on Monday to designate One Main Place, designed by SOM’s Gordon Bunshaft, as the city’s newest landmark. Beyond its waffled exterior, the 48-year-old International Style tower houses 19 floors of offices and a Westin Hotel spread out over its 33 stories.

Usually, buildings have to be at least 50 years old to be considered for landmarking, but officials made an exception for its high quality design and its singular place in Dallas’s history. The New Orleans–based owners sought the designation for one particular reason: historic preservation tax credits.

The gridded concrete and granite building, though, is already listed on the National Register of Historic Places. According to its designation report, One Main Place was supposed to be part of a three-phase redevelopment of downtown Dallas that was proposed in the 1960s. That superblock scheme, which would have replaced downtown with Corbusian Cities of Tomorrow, was never realized in full.

According to the Dallas Morning News, one preservation expert told the Landmark Commission that Bunshaft’s building, like Dallas’ pedestrian tunnels, merited protection because it reflects a specific approach to planning that prevailed in the city through the 1980s.

One Main Place is “the center and genesis of the tunnel system,” said Jay Firsching, a senior historic preservation specialist at Architexas. That system was proposed by Vincent Ponte, the Montreal urban planner behind his city’s famous tunnels that keep pedestrians out of the cold during long Quebec winters.

To become official, though, the landmark still needs the Plan Commission and City Council’s approvals.

Back east, Bunshaft’s SOM designs are getting recognition by another landmarks commission: In 2015, New York City’s Landmarks Preservation Commission added 28 Liberty, an office tower and plaza in Manhattan’s Financial District, to its roster of protected modernist buildings.