When it was unveiled in 1931, the elaborate mosaic-clad lobby of Irving Trust Co. at 1 Wall Street, an Art Deco skyscraper designed by architect Ralph Walker, was one of Manhattan’s most unusual interior gems. The Red Room, created by artisan Hildreth Meière, was sheathed in a dazzling pattern of orange and oxblood glass tiles, and laced with a web of gold and bronze lines. Closed to the public since 2001, the 9,000-square-foot mosaic installation is in the final stage of a 16-month, $1 million restoration, spearheaded by developer Harry Macklowe, who bought the building three years ago. (His firm, Macklowe Properties, is busy converting the rest of the 1.1-million-square-foot edifice into residences and retail.) When the vaulted space is once again revealed, the glowing results are sure to enchant a new generation of New Yorkers.