The Niagara Falls are located on the border between the US and Canada. With a boat, you can get very close to the waterfall. At night, they are lit with different colors. On the Canadian side is an entertainment district, which also has video arcades for young and old.
Quebec City is the founding city of Canada. Worth seeing is the building with the painting of 6 seasons and a castle on the mountain.
Ottawa is the capital of Canada, which made a very green impression. Worth seeing are the government buildings and when I was there, also the Independence Day was celebrated. In the evening, the government building was projected with colors and a film.
The city Toronto is located directly on a huge lake. When I was there, superheroes and disguised people besieged the city. The ComicCon had taken place and I did not hesitate to go myself.
I flew from the US to Montreal and made a day trip to Quebec City. Then it went to Ottawa and the Niagara Falls. The last stop was Toronto and I had plane back to Germany.
Canada is a huge country and to cover longer distances a plane is recommended.
I can recommend Rome2Rio to find the fastest and cheapest transport between cities.
In Ottawa, I can recommend the Jail Hostel Ottawa. An old prison that has been converted into a hostel.
In Canada there is the coffee chain called Tim Hortons. These have a filter coffee that tastes damn delicious 🙂