The Man in Seat 61 was started as a hobby by Mark Smith, a British railwayman. His fantastic site has the info on how to travel by train in over 100 countries. You can travel from London to Cambodia by train, for example, or from Cape Town, South Africa to Mwanza, Tanzania.
I’ve used this site extensively and I’m a big fan. I’ve taken the Eurostar from London to Paris. I’ve done quick trips in South Korea and the United States and overnight trains across Thailand and Sri Lanka.
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What’s the best train trip you’ve taken?