Mayor Anthony Williams on Thursday brought his sales pitch for a new $180 million central library to the D.C. Council, while his critics vigorously sought to preserve the historic but deteriorating building that the Martin Luther King Jr. Memorial Library now occupies.

In a rare appearance before a council committee, Williams said a new library on the site of the Old Convention Center — not an overhauled version of the existing building at Ninth and G streets NW, as others suggest — will provide “a new set of modern and effective tools to combat our education crisis.”