Getting to the pyramid itself requires a lot of leg power. You can either hire pedals to make it easier and faster, or walk a good 2km each way through the forest.
The Nohoch Mul pyramid is actually taller than Chichen Itza's El Castillo. Climbing it requires some skills as the steps are high and the structure is in a historical state. The reward is a nice view of the forest and nearby lakes all below you.
Coba is less touristy than Chichen Itza and is a very different experience. Before authorities decide to stop allowing climbs to the top, visit this on a day tour, combining with nearby Tulum.
Coin and bank note images from the Banco de Mexico.