Himachal is a quaint, peaceful state filled with abundant nature making travel that too summer travel very very memorable. Gada gushaini is full of lakes
Janjheli nature beauty of Himachal
Prini serene mountain spot
Churah valley mesmerising valley
Sangla natural scenery.
If you visit Shimla, and stay a little away from the Mall, it is quite peaceful. I had recently stayed in Bharari area, and my stay was extremely peaceful with a lovely view.
If you are going to the Mall, do take the heritage walk there.
Here are the details- https://bulbulonthewing.com/reasons-to-go-for-the-heritage-walk-in-shimla/
I would say Spiti Valley is the most peaceful and unexplored location within Himachal Pradesh. the only issue is you might be not get internet but that should be ok to not have for few days :)