1) "Travel" is a verb. "Trip" can be a noun or a verb. "Journey" can be a noun or a verb.
We can "travel to somewhere", but we can't "go on a travel".
We can "go on a journey" or we can "journey somewhere" although this use is not common.
We can "go on a trip", this means the same as going on a journey, or we can "trip", this has a different meaning and has nothing to do with travel.
2) A city is a very large town.