Hiking in Isalo is superb. Exploring the Canyon des Makis there a good chance of seeing lemurs grazing among the deciduous forest, and is a relatively flat and easy walk.
More challenging is the visit to the Piscine Naturelle. The first half an hour is a steep hike up the massif wall, rewarded by breathtaking views over the rocky valleys below. An oasis among the rocks, the piscine itself can be busy, but a dip in the cool water is the perfect way to relieve Isalo's heat.
Another pretty, but challenging hike is to the Cascade des Nymphes, and the black and blue pools. The slippery paths lead deep into the gorge, heading over, around and through the streams.
For very fit hikers, there is a walk across the massif from the Piscine Naturelle to the Cascade des Nymphes (we'd always recommend doing it in this direction to avoid a very long climb at the start!)
For those wanting a more sedate activity, the Isalo information center on RN7 has some interesting displays on the Bara, as well as explanations about the flora, fauna and geology of the park.
In the late afternoon your guide may suggest visiting the natural rock window to watch the sunset.