Welcome to this expansive, light-filled corner-unit condominium with two walls of windows and an ideal open floor plan. Enjoy the elegant living area with sophisticated lighting, and a separate dining room with the same blonde-wood flooring. The kitchen features an island with breakfast bar, pendant lighting, stainless steel appliances and ample storage space. The spacious bedroom features a custom walk-in closet and en suite bathroom. The large den, that can serve as a second guest room, is flooded with natural light. A convenient washer/dryer and powder room complete this superb offering. Nestled between K and H Streets, it's easy to see why neighbors love calling the magnificent 400 Mass home. Packed with amenities, residents enjoy a spacious community room, billiards room, fitness center, business center, 24-hour concierge, security, and more. The fabulous rooftop terrace with gas grills, swimming pool, and sweeping views of the city will be a favorite spot to unwind. Everything you need is at your doorstep with endless dining, retail, and entertainment options nearby. Commuting around or out of the city will be a breeze with Metrobus outside, I-395 one block away, and Gallery Place, Judiciary Square and Mt. Vernon Square Metros all only three blocks away. Garage parking space is available for rent at $230/mo, if needed.