Transit Town is an anime-exclusive location in Johto, more specifically located northeastwards of the Red Rock Isle. It is a port town that has one ferry going to Olivine City and another going to the Silver Rock Isle. The town has several buildings, but is mostly covered by trees. It also has a small, abandoned airport that is only used by Wings Alexander.
In the anime, Ash & Co. stop by Transit Town to take the ferry to Olivine City, but find that the ferry had already left and that they would have to wait a long time for the next one. They then head to the airport, recommended by a fisherman (in actuality a disguised Wings), where the famous pilot Wings Alexander and his Noctowl would take them to Olivine City.