All elements, arches, and emblazonry have been executed with delicacy. The square Chapter House is notable for its complex star vault lacking a central support and spanning a space of . This was so innovative at the time that prisoners, condemned to death, had to perform the task. The task was completed after two failed attempts. When the last scaffolds were removed, it is said that Huguet spent the night under the vault to silence his critics who thought that vault could not hold. The carved tracery decoration in Gothic style (including quatrefoils, fleurs-de-lis and rosettes) by Huguet in the ambulatory of the cloister of King João I now forms a combination with the Manueline style in the arcade screens, added later by Mateus Fernandes. In 1437, towards the end of his life, he started the construction of the mausoleum for King Duarte. This is a testimony to the fact that the monastery was never finished and are called therefore the Imperfect Chapels. They form a separate octagonal structure tacked on the choir of the church (via a retrochoir) and only accessible from the outside. The octagonal rotunda has seven radiating hexagonal chapels. There are several earlier Spanish examples of such a construction as the chapel of Alvaro de Luna (in the Cathedral of Toledo) and the chapel of the Condestable (in the cathedral of Burgos). The original design of Huguet was later altered beyond recognition by successive architects, especially Mateus Fernandes.