Bangladesh Rail travel:
Watching the news, you could be forgiven for thinking that Bangladesh was not so much a country as a disaster zone. But you'd be surprised. It is a fascinating country with a rich and varied history and at present fairly few tourists. Bangladesh has a largely British-built rail network linking most major towns and cities, including Dhaka & Chittagong. The network is divided into two halves, eastern and western, by the great rivers which divide the country itself. The western network is largely broad gauge, the eastern network largely metre gauge. Unfortunately, connections between these two networks are often poor.
Dhaka - Chittagong by train...
There is a good train service between the capital city, Dhaka, and Bangladesh's second city, Chittagong. Dhaka & Chittagong are both in the eastern half of the country on the metre-gauge train network, linked by fast daytime 'InterCity' trains and two good overnight trains with sleeping-cars. The high-quality InterCity trains are very popular and often leave full, so make reservations at the station as soon as you can.
Which class is best? AC seats and non-AC seats are in fact identical, and similar in layout & appearance to Indian AC Chair Class. The only difference is that AC seats are air-conditioned with sealed windows, non-AC seats have opening windows. AC first class has seats in compartments with sleeping berths for lying down and more room (yes, even though it's daytime train!). Photos of the Maitree express showing seats car interior.
How to buy tickets: Tickets go on sale 10 days before departure, and sales close 3pm the day before departure. In Calcutta, buy tickets at the Fairlie Place reservation centre at the Foreign Tourist Reservation Counter, open 10:00-17:00 Mon-Sat, 10:00-14:00 Sundays. In Dhaka, buy tickets at Dhaka Kamalapur station ticket office. Passports & visas must be shown when booking. Only one-way tickets can be booked.
Eastbound, customs and immigration take place at Darshana just inside the Bangladeshi border. Westbound, immigration controls take place at Dhaka Cantonment station.
Daily alternative train+bus link: There are two train links from Calcutta (Sealdah station) to the India/Bangladesh frontier, one to Gede and one to Bangaon. At Gede, the Bangladesh railway station of Darsana is a 1km walk across the frontier, for trains south to Khulna or northwards, but not to Dhaka. At Bangaon, it's a short walk across the frontier to Benapol station on the Bangladeshi side for a daily train to Khulna (but again, not Dhaka). Please confirm that foreigners are permitted to cross at your chosen crossing point.