I did this last year as my first century, after a few years of riding. It is pretty flat, with the exception of the climb up to the lighthouse in York and a little bit in Maine. But, just to warn you, the headwinds coming back were brutal. We were going about 13 mph in our grannies and my husband was so tired that he told me I "had" to pull him for awhile. So plan to go slower on the return part of the loop. It is very pretty.