Being one of those "trip to" choreographers, I think there are a number of reasonable places to draw the reference from. Certainly the obvious one of writing it while on the way to or from the particular location. Then it might also be to commemorate or honor an individual know by their location. I wrote one, Trip to Harlem, named after the tune I used, Drop Me Off in Harlem. to honor the passing of the great Duke Ellington. I am pretty sure there is no rule about it, and I'd so feel free to travel wherever your imagination takes you.