Would someone please explain to me how to successfully spread religions to cities in the latter part of the game? I know it’s a lot easier if there is no religion present in the city or at least one or two. Here is a good example, in my last game I was trying to spread Hinduism to a Persian city, in this particular city; it was the birth place of Judaism, Christianity, Islam, and Taoism. Is there no way possible to spread it with a missionary (because they kept failing), or does this Persian city accept the religion by its own accord?

Are there any particular wonders that I should aim for?

The only really good religious wonders come in the Medieval Age and they concentrate on putting your state religion to work rather than helping you spread anything. As far as I can see the Shrines also only provide commerce boosts rather than anything much else - unless I am missing something, and I probably am.

If a city has more than one or two religions, and is a Holy City to boot, the chance of failure is a lot higher than it is earlier on when things are still a free-for-all. Trade routes boost the chances of religion taking hold, but in general certain cities have a limit on the number of religions they can accept and I've never, btw, seen such a great holy city in my life (even Jerusalem can only count two religions founded there, and a third spread later!).

I take it, also, that you could click the button to spread the religion and Persia wasn't using Theocracy?

Persia was using Free Religion as their civic; spreading it to other cities within their empire was easier. I was astounded to see this particular city myself; I didn’t know it was possible for a city to have so many religions birthed within it.

Do like I did: Spread Missionaries around and start planting them in ally's cities. If you don't have your borders open, open them. Having a Mosque is another way to help spread religions via trade. Keep trying to spread it in Holy cities, eventually, it would go through.

Make sure they don't have Theocracy (even though there is no legit way of finding out), or else you won't get through. I use Theocracy not because it's a good way to stop infidel religions, but because it's my leader's favorite civic (Zara Yaqob).

Make sure they don't have Theocracy (even though there is no legit way of finding out), or else you won't get through.

You may find out what civics does a civ run if you examine the diplo- info screen.

The more religions that are already present in a city, the harder it is to add another with a missionary. It is possible to get all seven, but you'll get a lot of failures. Religions only spread naturally to cities with no existing religion, so that is generally not going to happen in the late game.

Make sure they don't have Theocracy (even though there is no legit way of finding out)

The civics of the AI are displayed as small icons in the top right hand corner of the diplomacy panel, and also in the foreign adviser screen. In any case, the button for spreading religion will be greyed out if the missionary is in a city belonging to a civ running Theocracy.

I use Theocracy not because it's a good way to stop infidel religions, but because it's my leader's favorite civic (Zara Yaqob).

You don't actually get any specific benefit from running your own leader's favourite civic.

As for wonders, the obvious ones are the Spiral Minaret, the University of Sankore, adn the Aposotlic palace.

The time that you get a 'favorite civic' benefit is when both you and the AI civ are both in the AI civ's favorite civic. As MrCynical has said above, there is no benefit to you for being in your civ's favorite civic.

If the other civ has Theocracy you wouldn't even be able to attempt to spread it, the missionary's "Spread Religion" button would be greyed out.

And yeah, to the best of my knowledge you'd just have to get really lucky to spread it to that city. If you're desperate and you don't mind cheating a bit, you could just save before you attempt to spread and reload if it fails. Otherwise, I'd just skip trying to spread there unless you really need to.

It's harder to spread religion to opponents cities than your own.

With such a religionsly strong city I would strive to capture it and then attempt to spread my own religion there afterwards or switch to one of the 4 alread there. Immediately after the conquest I would switch to Free Religion to get 20cp and happiness for the Holy Cities in one to get the city's economy up and running post conquest.

Just spam missionaries and keep trying. It's the only way to spread religion. I tend to use religions mainly as a diplomatic tool, but maybe that's a mistake. They seem to have major income potential, too.