I feel cities like rishikesh and Varanasi to cherish the beauty of Ganges, Cities like Shimla, Delhi,Mumbai and Kolkata are also there where you can find lot of things!!
From me!! Every place is best. Because when you travel solo you starts joining your own companion. Still you can go jaipur udaipur jaisalmer goa hamli gokarna varanasi
You can explore anywhere in India if you like solitude.India has a variety of culture and destinations.But it should be taken into account to respect the culture,the tradition,the festivals and most importantly the people of the particular destination
Rishikesh to Auli all along the path of Alaknanda would be a lovely experience. The green waters, picturesque mountains, white sand river beaches and roadside eateries present a beautiful ensemble. I have travelled a lot but this trip has been my favorite and most memorable. The fact that I did it on my Thunderbird with my love made it even more memorable.