The $150 million restoration of the 1,070-room Washington Hilton near Dupont Circle was unveiled yesterday. The work touched the entire property, and all guest rooms received an overhaul that included adding flat-panel TVs and updating the bathrooms. The hotel now offers 110,000 square feet of meeting space, including a new 30,000-square-foot multipurpose room called Columbia Hall. The new Heights Executive Meeting Center has nine meeting rooms and opens to a courtyard with views of the Capitol Building. The 36,000-square-foot International Ballroom, site of the only official inaugural ball for President Barack Obama, has been reconfigured to handle several groups at once; it now holds up to 4,200 for a reception.