Although often perceived as the site of Christians being thrown in with the lions to delight the Roman onlookers, this excerpt from Wikipedia's page about the Coloseum (
visit link) questions the accuracy of that idea:
"There are no historical records or physical evidence as to the use of the Colosseum, or any other amphitheatre, as a place of execution for Christians.
In the Middle Ages, the Colosseum was clearly not regarded as a sacred site. Its use as a fortress and then a quarry demonstrates how little spiritual importance was attached to it, at a time when sites associated with martyrs were highly venerated. It was not included in the itineraries compiled for the use of pilgrims nor in works such as the 12th century Mirabilia Urbis Romae ("Marvels of the City of Rome"), which claims the Circus Flaminius – but not the Colosseum – as the site of martyrdoms. Part of the structure was inhabited by a Christian order, but apparently not for any particular religious reason.
It appears to have been only in the 16th and 17th centuries that the Colosseum came to be regarded as a Christian site. Pope Pius V (1566–1572) is said to have recommended that pilgrims gather sand from the arena of the Colosseum to serve as a relic, on the grounds that it was impregnated with the blood of martyrs. This seems to have been a minority view until it was popularised nearly a century later by Fioravante Martinelli, who listed the Colosseum at the head of a list of places sacred to the martyrs in his 1653 book Roma ex ethnica sacra.
The Christian Martyrs' Last Prayer, by Jean-Léon Gérôme (1883)Martinelli's book evidently had an effect on public opinion; in response to Cardinal Altieri's proposal some years later to turn the Colosseum into a bullring, Carlo Tomassi published a pamphlet in protest against what he regarded as an act of desecration. The ensuing controversy persuaded Pope Clement X to close the Colosseum's external arcades and declare it a sanctuary, though quarrying continued for some time.
At the instance of St. Leonard of Port Maurice, Pope Benedict XIV (1740–1758) forbade the quarrying of the Colosseum and erected Stations of the Cross around the arena, which remained until February 1874. St. Benedict Joseph Labre spent the later years of his life within the walls of the Colosseum, living on alms, prior to his death in 1783. Several 19th century popes funded repair and restoration work on the Colosseum, and it still retains a Christian connection today. Crosses stand in several points around the arena and every Good Friday the Pope leads a Via Crucis procession to the amphitheatre."