On the road, above the arch, there is a viewpoint, which offer best views.
The arch is located near the Ardesh Gorge national park, which is located in the river canyon. This is a popular place for canoeing and kayaking. There are inexpensive options, for 1 hour, for example this one. Or search in Google for "pont d'arc rent canoe", there are a lot of suggestions. Here is also a beautiful map of this part of the river.
In general, this place is very beautiful and it makes sense to drive not only to the arch, but also along the canyon. If you are coming from the Lyon-Marseille motorway, then you definitely see the canyon.
Getting there: Best of all, by car, the coordinates of the large parking lot - N 44 23.016 E 4 24.816. There is also the possibility to park along the road here
N 44 22.983 E 4 25.123 (we did so). During summer months there is a free bus from the town of Vallon to the arch (20 minutes to go), departing from N 44 24.341 E 4 23.804. It is not so easy to get to the city of Vallon Pont d'Arc by public transport. The nearest railway stations Montelimar and Valence TGV, from there by bus number 76 (2 hours 20 minutes). Find here information on this bus.