You would need a basking area for most "slider" type turtles, but that is not the problem I see with your pond. The problem I see with your pond is that the ledge around your pond is not a tall enough barrier for turtles and they would eventually climb out and not be able to get back in and wander off.
I'm sure the pond in the restaurant had some sort of barrier to stop the turtles from climbing out.
I have a similar ledge on one side of my raised pond, and have had my turtles climb out. Fortunately they end up in our secure courtyard area where they were found again and placed back in the pond area. If not for the secure courtyard area they would have wandered off.
Our frogs also hop into the courtyard area nightly to hunt for bugs, and we sometimes noticed them too late, the hot sun had already gotten to them. The turtles are more resilient than frogs are out of the water for long periods of time. We solved the frog problem by placing a ramp beside the outside edge of the pond, and to my delight and amusement they adapted to it immediately. We eventually replaced the ramp with a large piece of driftwood that seems to work just as well as the ramp.