 The alabaster panes in the bottom parts of the aisle windows keep the interior cool during the fierce Italian summer, while the neo-Gothic stained-glass in the upper parts of the windows date from 1886 to 1891 and were designed by Francesco Moretti.The trussed timber roof was decorated in the 1320s by Pietro di Lello and Vanuzzo di Mastro Pierno, and was heavily restored in the 1890s by the architect Paolo Zampi and Paolo Coccheri to its current state.During the years 1335–1338 the transept was roofed with quadripartite (four-celled) stone vaults.