The Capela dos Ossos was built in the 16th century by a Franciscan monk who, in the Counter-Reformation spirit of that era, wanted to prod his fellow brothers into contemplation and transmit the message of life being transitory. This is clearly shown in the famous warning at the entrance Nós ossos que aqui estamos pelos vossos esperamos (“We, the bones that are here, await yours.").
The lugubrious chapel is formed by three spans 18.7 meters long and 11 meters wide. Light enters through three small openings on the left. Its walls and eight pillars are decorated in carefully arranged bones and skulls held together by cement. The ceiling is made of white painted brick and is painted with death motifs.
The number of skeletons of monks was calculated to be about 5000, coming from the cemeteries that were situated inside several dozen churches. Some of these skulls have been scribbled with graffiti. Two desiccated corpses, one of which is a child, dangle from a chain. And at the roof of chapel, the phrase "Melior est die mortis die nativitatis (Better is the day of death than the day of birth)" (Ecclesiastes, 7, 1) from Vulgate is written.