First, the site, El-Araj, is only one contender to be the ancient city of Bethsaida. The other is et-Tell. Second, there is no direct indication — such as an inscription — in the ruins of the church that it was dedicated to Peter. The inference is based on an account by an eighth-century visitor.
Read the whole article for details.
Past posts on the two contending sites for Bethsaida are here (cf. here) and links.
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