Perkins Memorial Tower

Nice spot.
1) The Tower offers a panoramic, 360 degree view of the Hudson River Valley.
2) There are maps all around the tower to aid you in picking out the names of adjoining towns and mountains.
3) It is completely free.

Personally, I found the view from the rocks in front of Perkins Tower offer a better view than from the top of the tower itself. I think there is something about the glass separation that takes away somewhat from the experience.
But with that said, Perkings Tower offers a panoramic, 360 degree view of the Hudson River Valley — and there are maps all around the tower to aid you in picking out the names of adjoining towns and mountains.

Make your way to the top of Perkins Drive to Perkins tower. You can make it up by taking the 10-​minute drive up, by biking, or the 1-​hour hike up along the Appalachian Trail. When you get to the top, witness majestic views of Bear Mountain and the surrounding area. Meander along to the South facing side of the tower and you can walk along big rock boulders to get a nice view of the water and mountains. Just be sure to watch your step so that you don’t slip and break something. Have a snack or lunch? There’s plenty of old wooden benches in the area that you can sit and relax on.
And one last thing. Try to come before 11 AM to secure yourself a spot. Crowds usually start to come by then, and by mid afternoon (~2 PM), the lot can be packed and you’ll be forced to park along the road if available.

Perkins Tower is the prize for reaching the top of Perkins Drive be it by bike, moto or car or some other wheeled vehicle. When open do take a climb up into it. Not only will you be afforded some wonderful views of Bear Mountain Park but on a clear day one can see Manhattan in the distance.
Along the walls of the interior’s climb are lots of propaganda to read relating to its building, purpose, backers-​lots of history for this region the Lower Hudson Valley, NY. Perkins Drive is a gorgeous road which circumnavigates the mountain and then lets you choose a left and back to the Bear Mountain Circle and Bridge or a right which also meets up, with the Palisades Parkway. Eeeny meeny miny moe. Does not matter as you might want to attempt all points of entry and egress on your first day. From the tower you can take lots of photographs of the changing seasons and watch the weather roll in. It is, along with the Drive, closed in Winter but in Autumn is spectacular with its charming colorful foliage.
So it is a Tower tower but it is also a landmark that beckons crotch rockets, laid back Harley folks, minivans full orthodox families and we all get along up there. Quite magical… No entry fee for the park, nor the drive, nor the climb in the tower. Not a bad way to spend a few hours getting to know this breath-​taking little corner of the world. Enjoy.
The Man :
And just a little more to whet your BMP appetite: