Spiti is Himachal without the crowds — a cold desert of ochre cliffs, thousand-year-old monasteries and villages that sit above 4,000 metres. It is harder than Manali and less commercial than Ladakh, which is exactly why groups that have done both keep coming back to it.
The Shimla side (via Narkanda, Sangla and Nako) climbs gradually and is far better for acclimatisation. The Manali side over Kunzum La is dramatic but gains altitude fast and only opens from roughly June to October. The ideal group plan enters from Shimla and exits via Manali, so nobody drives the same road twice.
Key Monastery above the Spiti river is the photograph everyone comes for. Kibber, Langza, Komic and Hikkim sit even higher — Hikkim runs the highest post office in the country, and posting a card from there is a group ritual by now. Dhankar and Tabo are the older monasteries and deserve an unhurried morning.
Homestays are the norm and rooms are limited, so a group of more than six should book ahead rather than arrive and search. Fuel is available at Kaza and Powari only, and cash matters — ATMs are unreliable. Nights are cold even in July, so a warm layer belongs in every bag regardless of what the plains weather suggests.