Wodan
Deity
I remember someone asking about this could happen in an old thread, and it just happened to me, and here's how...
The Celts had founded a religion, and were in a losing war against Rome. They had a second GP dorking around their capital's tiles, not doing anything, just moving around. Rome captured the GP and the capital too. Then, Rome moved the captured GP into that city (probably because it was nearest) and established the new religion (which they were allowed to do because they had not founded a religion yet).
[I'm assuming that's what happened because, while I had units right there, "watching," I didn't notice anything else, and the captured GP was there and then it was gone with the founding of the new religion.]
So: two religions founded in that one city. Not that either of them are doing anything... the old religion is fading out and the new one isn't going anywhere because obviously Rome hasn't built any shrines or temples or anything, so isn't getting any faith.
The Celts had founded a religion, and were in a losing war against Rome. They had a second GP dorking around their capital's tiles, not doing anything, just moving around. Rome captured the GP and the capital too. Then, Rome moved the captured GP into that city (probably because it was nearest) and established the new religion (which they were allowed to do because they had not founded a religion yet).
[I'm assuming that's what happened because, while I had units right there, "watching," I didn't notice anything else, and the captured GP was there and then it was gone with the founding of the new religion.]
So: two religions founded in that one city. Not that either of them are doing anything... the old religion is fading out and the new one isn't going anywhere because obviously Rome hasn't built any shrines or temples or anything, so isn't getting any faith.