Georgetown’s latest hotel — The Graham — opened to the public May 3, after a series of top-drawer opening receptions. The 57-room boutique hotel boasts the only rooftop lounge — the 3,000 square-foot Observatory — in Georgetown that is open to the public. The hotel named its signature restaurant A.G.B. After all, Georgetown is the neighborhood where inventor Alexander Graham Bell once called home. The Volta Bureau, the non-profit he founded, is on 35th Street. Generating lots of favorable buzz, the Graham’s rooftop Observatory lounge has already gotten on a Forbes list of rooftops to check out.