Given the story, I think we can safely assume that the different pony kinds are shut up in their own enclaves and not travelling, shipping or talking one another. (It's still an open question if the three settlements shown are the only pony settlements.) But all that used to happen in the old world and we know that several old world structures and locations still exist. I've heard that Zephyr Heights is built on what used to be Canterlot. True or not, it still has an old station for travelling between settlements. Ponies used to have ships, as seen on multiple occasions in FiM, so the lighthouse (and location of Maretime Bay) could just be a remnant of old Equestria. That seems more likely as we never see or hear of the lighthouse being used.
"If all mankind minus one, were of one opinion, and only one person were of the contrary opinion, mankind would be no more justified in silencing that one person, than he, if he had the power, would be justified in silencing mankind."
~John Stuart Mill~
Given the story, I think we can safely assume that the different pony kinds are shut up in their own enclaves and not travelling, shipping or talking one another. (It's still an open question if the three settlements shown are the only pony settlements.) But all that used to happen in the old world and we know that several old world structures and locations still exist. I've heard that Zephyr Heights is built on what used to be Canterlot. True or not, it still has an old station for travelling between settlements. Ponies used to have ships, as seen on multiple occasions in FiM, so the lighthouse (and location of Maretime Bay) could just be a remnant of old Equestria. That seems more likely as we never see or hear of the lighthouse being used.
"If all mankind minus one, were of one opinion, and only one person were of the contrary opinion, mankind would be no more justified in silencing that one person, than he, if he had the power, would be justified in silencing mankind."
~John Stuart Mill~