Bike tours can be a great way to see the countryside up close at a leisurely pace. I love trains but scenery goes by pretty fast! Many tours are available so are self guide, others are organized and can include a vehicle that carries your luggage and provide refreshments, so you have a lighter travel experience.
Discover France has a large selection of tours including ones geared especially for seniors. From Brittany and the Loire Valley to Provence, or a Bordeaux wine tour.
See also 57Hours on my Travel Info page. Some research is need on them — they appear to be just a booking agent rather than a tour company.
