Keep in mind that DC has a building height limit of 130 feet in commercial areas, so that caps the height around 10-11 floors. I agree that the building at 1331 L St. NW is nothing special in terms of looks, but it's built about as tall as it legally can be. I also did some digging and it's not clear to me who actually owns their DC HQ building. There are a bunch of LLCs involved so it may ultimately be CoStar as the owners, but it could be that their leasing it from a completely separate entity. The land they just bought is registered under Costar Realty Information Inc, so I'm guessing that they are just leasing the building in DC.