Climbing Artificial Walls is relatively safe. Here is a Quora Link to Artificial wall safety.
This is usually done in a climbing Gym where the holds are attached to textured walls. They can either be indoors or outdoors and will usually cost you money either as a member or guest.
here is a basic list of some LA gyms:
There are also local maverick areas. these are closely guarded secrets to the local communities and generally require introduction by one of the locals who will vouch for you. They are set up under bridges or on other inconspicuous areas not clearly visible by general passers by. The holds are glued in place by local climbers and may even include bolted routes. The key to their survival is secrecy as the local city maintenance are obligated to remove any such areas if found. Frequently the holds are either artificially molded or actual stones glued in place. I have seen some that circumvent drainage tunnels in completion. Some of the best workouts are found in these grounds but safety may be a little compromised due to the conditions.
