Apart from cyclists threatening to mow one down (selfish shower), walking canal towpaths is a civilised way to exercise and view industrial architecture. No cars to contend with, sometimes magnificent scenery to feast the eyes on and many places of interest to see close to the canal.
Before the coming of the railways canals were the equivalent of today's motorways for moving the raw materials and products of industry. The railways did for much of the canal system, indeed the railway companies often bought out the canals and laid their tracks close to them. Over the last 30 years many derelict canals have re-opened, thanks to an army of volunteers digging out huge quantities of silt, plants and rubbish. Lock gates have been replaced. Some places on canals look like visitor attractions, but a small price to pay for the solitude to be enjoyed away from them.
It is possible to walk along the towpaths of derelict canals, in some places the former canal is a series of stagnant ponds, in others the cut is as dry as a bone.
Canals in cities are just as interesting as those meandering through the countryside. Over the years I have walked most of the towpath between Little Venice and Limehouse in London. Away from the hustle and bustle, nevertheless there is much to see, admire and enjoy.
Below in a link to an article on touring London's canals. The page has links to more articles and websites devoted to canals.