Sightseeing from a bus is great but you miss a lot! Sightseeing on foot is OK for the first couple of hours - then your feet hurt, your shoes don’t fit, you develop heel spurs and your ankles don’t like cobblestones.
Paris was one of the first to come up with rental bikes - it now has 20,000 bikes at 1800 stations all around Paris. You can buy a one-day ticket for less than CA$2.50 or a week-long pass for just over CA$11.00. You can use the bikes for as many times ay you like and for each bike the first 30 minutes is free. Thereafter it’s about CA$1.40 per half hour.  
Bike rentals are becoming more and more common. The Mayor of London has been promoting bike rentals for a while but leave it to the car rental boys to go to the next level.
Hertz announced this week that you can rent an electric bike with a top speed of 15mph from their location at Marble Arch for CA$32 per day - and they give you full training, a lock, optional helmet and a copy of the AA Leisure Guide to London with suggested bike rides around the City.
The only problem I see for North Americans is remembering to look right ....or is it left?