The Pool at Residence Inn Washington National Mall
The pool at Residence Inn Washington, DC/Capitol is endorsed by professional travelers. Of the 3 publications that we monitored, 2 mentioned the pool, like Oyster and Time Out.
Residence Inn Washington National Mall 
Oyster
Time Out
Oyster "'s compact southwest quadrant, this 13-story hotel with 233 large, suite-style rooms opened in 2005 and remains popular with businesspeople and lobbyists during the week (it's encircled by federal buildings) and families on weekends (spacious suites, free breakfasts and dinners, indoor pool)"
Time Out "The hotel is sumptuous in every detail, from the gorgeous spa, indoor pool and top-notch restaurant to the bed linens and bathroom toiletries"
