This small, hemispherical dome, possibly constructed at the beginning of the 16th century, uses Brunelleschi’s opus spicatum or herringbone brickwork technique. Discovered in 2013 during works to enlarge the museum, the dome is an example of the opus spicatum, or herringbone, brickwork technique Filippo Brunelleschi contrived to construct the huge dome of the cathedral without using rib vaults. The pattern in which the bricks are laid stop them slipping down during construction and allow them to follow the curve of the dome without support. Currently it is impossible to say whether Brunelleschi was involved in building this smaller dome or not, possibly as a trial run for the great work he embarked on in 1420, because initial carbon 14 dating places it at the beginning of the Cinquecento. It is, however, a splendid example of the technique perfected by the famous Florentine architect.