Hey Peisun, I'd suggest you plan a trip to North India. It will difficult to travel in summers to any other place. From New Delhi, you can also plan for Kerala, South India, all you have to do is take a flight to Kochi and then hire a cab or take the local buses to travel around the state. There you can cover places like Munnar, Thekkedey, Alleppey, and Varkala. Up in North, you can plan a 10 day trip to Spiti Valley. There are 2 ways to reach Spiti, you can reach Manali and take a cab for the place or you can via Shimla and take the local bus to Reckong Peo and from there to Kaza. Another place I can suggest for 10 days is Ladakh. You can go for a trip to Ladakh by taking a flight from Delhi to Leh. 10 days will be good enough to cover Ladakh.