travel vs travel to

travel is a noun but travel to is not a noun.

Word	Noun	Adjective	Verb	Adverb
travel	Yes	No	Yes	No
travel to	No	No	Yes	No

As verbs, travel to is a hyponym of travel; that is, travel to is a word with a more specific, narrower meaning than travel:

Other hyponyms of travel include junket, junketeer, visit, journey, travel, ply, run, commute, peregrinate.

travel (noun)	travel to (noun)
the act of going from one place to another
self-propelled movement
a movement through space that changes the location of something

travel (verb)	travel to (verb)
change location; move, travel, or proceed, also metaphorically	go to certain places as for sightseeing
make a trip for pleasure
travel upon or across
undergo transportation as in a vehicle
undertake a journey or trip
travel from place to place, as for the purpose of finding work, preaching, or acting as a judge