The Welland Canal is the way ships move between Lake Erie and Lake Ontario, to bypass Niagara Falls. At lock 3 in St. Catharines, there is a visitors center that includes a restaurant, museum, souvenir shop (of course), and an observation platform.
When arriving, first check the daily schedule of ship arrivals. Since it takes about an hour for one ship to go through this lock, you may be here for a while!