Petrusakten
The site for crucifixions in the Circus would have been along the "spina" ("spine"), as suggested by the 2nd century Acts of Peter describing the spot of his martyrdom as "inter duas metas" ("between the two "metae" or turning-posts", which would have been equidistant between the two ends of the circus). However, the existing Latin manuscript of the Acts of Peter belongs to the 6th-7th century and is believed to be a 4th-5th century translation of the original Greek. The Greek text has survived in 9th century and later manuscripts only, which does not allow to determine the exact date of this description precisely. The obelisk at the centre of this circus's "spina" always remained standing, until it was re-erected in Saint Peter's Square in the 16th century by the architect Domenico Fontana. The obelisk was originally brought to Rome by Caligula.