+1 Galastel; your "barabarian" might find those towering buildings just foolish, he doesn't automatically see any advantage in them at all, they isolate people, they are hard to climb, you are trapped in them if attacked, and on and on. The same for other technology, you need to understand that he doesn't understand the problem these "amazing" things actually solved in our past, and without understanding what they DO, they may seem to him a frivolous waste of time and effort.
Primitive tribes tend to be relentlessly social people, other people are their whole life, their entertainment, absolutely necessary for their survival. The tribe is their partnership and they spend their day doing their part, whatever that is. They wouldn't like this modern world where people are independent, enjoy being alone, don't talk to each other and are actively unfriendly, always in a rush to be somewhere as if life is a constant emergency. Some of the conveniences might be fun (moving fast, flying, food on demand), but they would probably tire of the amusement park aspect and want some company and normality.
Also you have to deal with human psychology: Amazement doesn't continue; after about 90 minutes, an intelligent person will just accept they don't know how things work, but also will recognize these new people aren't creating these new things with any effort, they take everything for granted, and so should they. An intelligent person will switch from amazement to "exploration and experimentation" very quickly, and learn the basics very quickly. They will be riding the subway within days.
That is the basics of acclimatization; your primitive's amazement will be fairly rapidly replaced by the thoughts, "what useful purpose does this serve, how do I control it, how does it communicate to me?"
Simple things like an elevator will be learned quickly. If he can't read numbers, then remember primitive people that don't rely much on a written language rely on their memory; they have a phenomenal positional memory and navigational sense. So he might not know "27" means the 27th floor, but he will accurately memorize the symbol and the position of the button and the sequence of buttons to push on first exposure.
It is fine to write about amazement and wonder upon first exposure, but it isn't realistic for that to persist for more than a day or two. Then your primitive will likely settle into an analytic problem-solving mode of thought for dealing with his new environment. He will be inured to all new amazements and see them all for what they are -- tools.
And finally, he will likely be pining for his old and more familiar environment, for two reasons. First, because to him, that required far less mental work to get through the day. Second, due to a lifetime of training, he felt emotionally rewarded by the daily accomplishments of his old life, like hunting and killing dinner, connecting and playing or joking with people, the constant physical exercise of walking and working, the mutual admiration society of his tribal peers that produces a tangible sense of familial belonging. All those things have been taken away from him, especially people that understand him well enough to be actual friends.