Calcutta had, until recently, a reputation for squalor and poverty, but in this vibrant city of 13 million inhabitants sits an important part of east India's historical heritage in buildings such as the Marble Palace, the Botanical and Eden Gardens, the Victoria Memorial, and in the museum. This delta is home to one of eastern India's many and diverse ecosystems - Sunderbans with its huge mangrove forests and tiger reserve.
Further to the north the Himalayan foothills are perfect for trekking. One of the key areas is Darjeeling, where you can stay in a lodge surrounded by rolling tea plantations and spectacular views of the Himalayas. From here you can continue north into Sikkim for a few days walking. Once an independent Himalayan Kingdom like Bhutan, the state is scattered with monasteries along what was once the main Himalayan trade route.
Another short flight from Calcutta is Assam, where we recommend joining a river cruise along the Brahmaputra river to visit Kaziranga National Park and (hopefully) see indigenous one-horned rhinos. Further north and east still the forested hills are populated by tribal people more Burmese than Indian in appearance and culture.
Finally, for yet another variety of eastern India holiday, Orissa's temples and beaches are well worth exploration.