The Trans-Siberian Railway is a single train line that crosses nearly the complete length of Russia, from Moscow to Vladivostok. It covers a total of 5,772 miles, running from Europe to Asia. Unlike the longest flight in the world, which just began transporting passengers in 2018, the Trans-Siberian Railway started its business in 1916.
Anyone who has taken this long journey, or even just part of it, will tell you that it travels at a rather slow speed, passing through some amazing, remote areas of Russia. You don't have to make the full journey without stopping. Instead, you're suggested to get off where there are attractive views, since it stops in some pretty fantastic places. But you certainly can take the full journey non-stop. If you do, the trip will take about 144 hours—six full days!
You can book tickets with travel agencies. You can also make the booking online and tickets will be sent to your hotel or personal address. Children under 4 years old accompanied by adults can travel free, but cannot take up a seat. A child ticket needs to be bought if you want to get a seat for the child.
There are longer railway services in the transportation world, but only one of them is a passenger line as some longer routes transport goods, not travelers. This railway may not be the fastest or the most modern, but it's clearly still an important player in the transportation world!