We had a lovely stay at Marks place. Looked exactly like the photos. Very modern and clean. Sheets and towels were lovely, very soft. Spacious fridge freezer. Lovely shower. We found the washing machine and tumble dryer very useful. Only point is the noise from upstairs - didn't disturb us too much except for the last night where they were up past half three in the morning watching tv.
Very easy to get into the centre of Washington and we loved Georgetown nearby. Washington is great for gluten free food including trader joes nearby. Uber's very easy and cheap.