Final answer:
A church built over the tomb of a martyr is known as a martyrium. Significant examples include the church of the Holy Sepulchre in Jerusalem and the expansion of the St. Peter's Basilica over the believed grave of the apostle Peter.
Step-by-step explanation:
A church or other edifice erected over the tomb of a martyr is referred to as a martyrium. This term describes a structure that marks the burial place of a martyr, someone who has been killed due to their religious beliefs. The tradition of building over the tombs of saints and martyrs has a long history within Christianity and can be traced back to significant historical figures such as the Roman Emperor Constantine, who had the altar of his fourth-century basilica placed directly over the believed grave of the apostle Peter. This practice served both as a form of honor and as a means to inspire the faithful.
The adaptation of churches to house relics of saints and martyrs was also prominent. Churches were either rebuilt or specially designed to accommodate these sacred remains, such as the church in Autun built for the relics of St. Lazarus, or the Basilica of San Miniato al Monte in Florence, which was designed to allow visitors to visit the crypt housing the relics of Saint Minias. The church of the Holy Sepulchre in Jerusalem, for example, includes a rotunda covering the tomb of Christ, echoing the architectural traditions of Roman mausoleums.