"Today, a penthouse can even be on the ground floor, if it's all tricked out and boasts luxury amenities not found in the building's other units," Cathie Ericson wrote for Realtor.com. "These might include upgraded appliances, increased security, fancier finishes, a larger balcony, oversize windows, a breathtaking view, a larger floor plan, and a private entrance."
Source: Realtor.com