I’m not sure that there is one word that will fit all occasions/locations. To me, what you’ve described is something like someone “shooting the breeze” but with their eyes and thoughts. In other words [**watching the world go by**][1] :-D

> to relax outside by just looking at the people around you

One would perhaps [contemplate][2] nature 

> contemplate: 1. to look at or view with continued attention; observe or study thoughtfully
>-to contemplate the stars

and [survey][3] the traffic?

> to view or consider comprehensively

the person would maybe be [observing][4] life around them, overall.

> to watch something or someone carefully:
She spent her career observing animal behavior.
>-On their field trip, the students observed how a newspaper was put together.




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I was curious to find out if there is a single word for the idiomatic expression "watching the world go by" and decided to search EL&U. I came across [**flâneur**][5], via [@Matt's][6] answer to the question [What’s a word for someone who appreciates the little things?][7], serendipitously! 
  
>a person who walks through public spaces, watching and appreciating the world going by

defined by Cambridge dictionary as
>someone who walks around not doing anything in particular but watching people and society:

 >- She wanders around with her camera, a flâneur with a keen eye.
 >- Lisbon is a city built for the ultra-relaxed, aimless flaneur.

This French loanword is new to me and I assume it's likely not widely known by others either (1,360 Google search results). I think it has a nice ring to it. Despite not involving idly sitting, it appears to be something people should take on to relieve the stress of modern living. 
[What is **flaneuring**? The walking trend that will leave you relaxed and inspired][8]

['I needed more quiet in my life. The French art of **flaneuring** showed me the way.'][9]  

 


  [1]: https://www.ldoceonline.com/dictionary/watch-the-world-go-by
  [2]: https://www.collinsdictionary.com/dictionary/english/contemplate
  [3]: https://www.merriam-webster.com/dictionary/survey
  [4]: https://dictionary.cambridge.org/dictionary/english/observe
  [5]: https://dictionary.cambridge.org/dictionary/english/flaneur
  [6]: https://english.stackexchange.com/users/53506/matt
  [7]: https://english.stackexchange.com/questions/130214/what-s-a-word-for-someone-who-appreciates-the-little-things/130247#130247
  [8]: https://www.today.com/health/what-flaneuring-how-can-you-take-awe-walk-t195686
  [9]: https://www.nbcnews.com/better/lifestyle/i-needed-more-quiet-my-life-french-art-flaneuring-showed-ncna1066636