Alexander's Hetaroi
Deity
I'm assuming though it can still reach a foreign city that is inland, but who has built a harbor, as long as it passes through the harbor to reach the city center. At least I would hope so.I mean, I guess. It seemed obvious to me, but fair enough. I guess the ability doesn't specifically say "water only". For what it's worth, your trade route actually can go over land from your city to the water. It just can't cross other land.