Bull Hill (or Mount Taurus, if you're fancy) is one of our go-to hikes near Cold Spring. The views from the summit are genuinely spectacular - maybe some of the best river views in the entire Hudson Valley, and that's saying something.
The trail is about 5 miles round trip with some real elevation gain. There are rocky sections that require careful footing, especially after rain when things get slippery. We'd rate it solidly moderate - you'll get a workout, but it's doable for most hikers who are in decent shape.
What we love about this trail is the variety. You start in the woods, pass through some open meadows, scramble over some rocks, and then boom - you're at the summit looking down at the river and the valley spreading out in every direction. We always pack lunch and eat at the top. It's one of those spots where you just want to linger.
Fair warning: since it's close to NYC, it gets busy on weekends. We've started doing Saturday morning hikes here, leaving early, and that makes a huge difference. Cold Spring is right there for post-hike food and wandering, which is half the fun of a day trip here.