here's a
link to topographical map of the area. You can enlarge or move it along as needed. It'll give you a good sense of what the area will be like, and which roads best snake through narrow breaks if you want to ride east/west across the grain.
You'll not thay there are two main valleys, the Hudson (obviously) and the "Central Valley" just wast of the Mass border. If you want to avoid hills either one of those slots which will get you to route 22, ride that north, then find an escape back west, and work your way south on that wide sloping plain. Or don't go east to the Central Valley, and you have a large expanse of flattish or gently rolling terrain bounded by the ridge to your east, an the river to your west.
Years ago we used to ride this area navigating by our shadow knowing the east and west boundries. We'd ride the area as a small group of 2-5 riders without maps or guides following the rule that whoever was in front an an intersection was in charge and could take us in any direction. After a while, we'd check our watches, figure out sort of where we were, and be more organized about getting back to the start.
Obviously, I'm biased because it's sort of my back yard, but this is one of my favorite day and weekend riding areas anywhere.
either up from NYC for a double century weekend, or using the train to do the entire ride in the area.