Last night, Dr Ian Walker asked this question via Twitter.
Using Dr Walker’s home town of Bath, England as a starting point, I responded with an example from Google Maps that looked something like this.
With Google Maps, you can add destinations you’d like to add, and even make your starting and ending point be the same place, like this:
Click on “Add Destination” then “Get Directions.” Once you do that, you can also drag the routes around to fine tune to include or avoid certain roads and paths, if you prefer. Here’s a British example giving a 36 mile circular route between Bath and Bristol.
I don’t know that area so I have no idea how realistic that route is, so I’ll generate a ride for an area I do know: Longmont -> Gunbarrel -> Erie -> Dacono -> Longmont. This gives a 40 mile loop through the flat part of Boulder County and western Weld County, Colorado.