Our modern address system is ubiquitous, and it's hard to imagine a life without street names and house numbers... at least in the developed world. But how did people in ancient times do the things we take for granted today?

How would you send mail, in let's say the Roman Empire?
How would you meet your Athenian lover who lives far away? How would you arrange to meet up in the first place, without fast communication means?

I can imagine rural areas were chaotic as they still are today in many places. But I'm more wondering about huge well planned cities like Ur, Yinxu, Rakhigarhi, Babylon; Rome, Athens, Alexandria, and even later ones such as Baghdad and Beijing or even Tenochtitlan.

What address systems were used in ancient times, if any, and when did our modern address system arise? I'm basically interested in anything that isn't the modern thing we're used to.