Hamilton is a good base for the western end of the Golden Horseshoe. Niagara Falls and Niagara-on-the-Lake are both about an hour east — easily a long day with stops along the QEW. Burlington and Oakville are 20 and 30 minutes north along the lake, with the Royal Botanical Gardens spanning the Hamilton-Burlington boundary.
Heading west, Brantford (an hour) for the Bell Homestead and Mohawk Chapel; Paris, Ontario, a pretty river-and-stone town just beyond Brantford; and Stratford (about 90 minutes) for the Shakespeare Festival. Toronto itself is an hour east by GO Train from Hamilton Centre, with frequent service on weekdays and weekends.