A French Village in the hills near Da Nang, built by the French during their time in Vietnam? Sounds enchanting.
I did not have a lot of time to do research prior to this trip, and a couple of things I read about the sites were not clear, but I would say that unless you like Disneyland, touristy sites, you can skip Ba Na Hills altogether. I would classify Ba Na Hills as an amusement park, although a very unique one. This is why I am conflicted as to whether I would recommend someone to go here or not.
There ARE a couple of positives. First, there are the cable car lines you take to go up the mountains which have won various world records. The view is nice going up and down. The system looks very well maintained and efficient. The cars are nice, modern, and clean.
My first stop was the Golden Bridge.
It was cool to see, but it is incredibly packed with tourists, so hard to get a good picture, and if you go on a foggy day like I did, you will not get a good photo, or view of the bridge. The bridge itself is new.  From the photos I saw of the bridge before going, I thought it was a historical site, not part of an amusement park. Next you walk around what appears to be a faux French Garden and village.
While it was impressive to see the French architecture on such a large scale in Vietnam, unless you never plan on going, or have never been to France, there is no point in going just to see this. After having gone, I still do not know whether the French actually built or lived here historically, and if they did, what part of Ba Na Hills was faux, and what was authentic. I visited a wine cellar with signs that said they were built by the French in the early 1900s, but to me it looked like a replica.
We had an unremarkable lunch and then checked out the amusement park – various rides, games etc. So should you go to Ba Na Hills or not? Overall, I would suggest you skip this. IF the historical significance of the place was made more clear, or was the main focus, and more info was given, then it would be a “go see”. However, simply as an amusement park, I do not think one comes to Vietnam to see an amusement park.
Next stop was Marble Mountains.
At Marble Mountains you buy a ticket to enter, and can either ride the elevator (pay up and down), or take the steps. Once at the top, there are great views of the city of Da Nang, pagodas, and the caves.
If you Google the caves, you will see beautiful interiors. The problem is there is no warning that you have to be very fit to see them. The entry to one of the caves was steep, slippery, crowded, narrow, and we were told, only had one way in and out, which presents a problem given the crowds. We braved two sets of steps, and then we were presented with a third set which required something more similar to rock climbing, and at that point, were told that there were 5 more sets of such steps, and so I turned around. This is not suitable for young children, people with disabilities, seniors, or anyone not prepared for a workout.
You can Google the pictures and decide for yourself if it is worth the effort to see, but be prepared with proper shoes and clothing.
Next stop, Hanoi.