A letter of advice to Augustine of Canterbury from Gregory the Great sometime after 596 C. E. Augustine was been Prior of Saint Andrews Monastery in Rome when the Pope sent him to England in 596 to convert the Saxon kingdom in Kent.   Note Gregory’s rationale for blending traditional pagan culture (buildings and folks festivals, for example) with the Christian faith.

Tell Augustine [of Canterbury] that he should by no means destroy the temples of the gods but rather the idols within those temples. Let him, after he purified them with holy water, place altars and relics of the saints in them. For, if those temples are well built, they should be converted from the worship of demons to the service of the true God. Thus, seeing that their places of worship are not destroyed, the people will banish error from their hearts and come  to places familiar and dear to them in acknowledgement and  worship of the true God. Further, since it has been their custom to slaughter oxen in sacrifice to the demons, they should receive some solemnity in exchange. Let them, therefore, on the day of the dedication of their churches, or on the feast of  those martyrs whose relics are preserved in them build themselves huts around their one-time temples and celebrate the occasion with religious feasting. They will sacrifice and eat the animals not any more as an offering to the Devil, but for the glory of God, to whom, as the giver of all things, they will give thanks for having been satisfied. Thus, if they are not deprived of all the exterior joys, they will more easily taste the interior ones. For surely it is impossible to efface everything all at once from their... minds, just as, when someone wishes to reach the top of a mountain, he must climb by stages and step by step, not by leaps and bounds... Mention this then to our brother the bishop [Augustine], that he may dispose of the matter as he sees fit according to the conditions of time and place.