Hi Julia, thanks for asking me . I dont work in tourism so i cant introduce the best tour in Hanoi. But i can tell you as a Hanoian. There are many nice places or spots you can visit when you come here: The Temple of Literature (V?n Mi?u) , the oldest university in Vietnam (1070); One Pillar Pagoda (Chùa M?t C?t); Sword Lake ( Hoan Kiem Lake) in the center of Hanoi; Flag Tower of Hanoi; Ba Dinh square; West Lake, the largest lake in Hanoi; Grand Opera House; The Presidental Palace Ho Chi Minh...Beside that Hanoi has over 600 pagodas and temples, many streets with original street layout and architecture of old Hanoi, each street then had merchants and households specialized in a particular trade, such as silk traders, jewellery, etc that the foreigners very like. You can go to some musems and popular markets, enjoy many special Hanoi food.
There a website about Hanoi for the foreigners who have come here to join and share their experiences, i think it will be useful for you if you want to visit our city:
Hope it can be helpful in some ways. Best regards.