In reply to Dangerous Dave:
It isn´ t easy to find a more suitable way to make them without being more expensive, huge and ugly. They have to be out from the rock about 150mm, wide enough for big feet, stop the feet sliding off sideways and strong enough they don´ t bend. Welding is expensive and prone to corrosion so one-piece glue-in is the way to go.
You´ ve only got to look at the commercially available options to see what you end up with (they are called chamber steps for installing in sewers and similar)!