Michelangelo’s “The Last Judgment” is undergoing its first major restoration in three decades. The imposing fresco of heaven and hell dominates the Sistine Chapel. The chapel will remain open to visitors during the three-month cleaning. The Vatican Museums said in a statement on Monday that the scaffolding will partially obstruct the view of the fresco. The cleaning will remove microparticle buildup on the plaster from so many people visiting each day.