The transit areas are defined for travellers which are making en route stops while changing flights and so on. This way these travellers don’t have to go through border controls as they have not formally entered the country they are transiting through.
Still, these transit areas are the territory of the country where the specific airport is located. Therefore the country’s laws still apply there. In case a crime is committed at the airport, the country where the airport is located will be prosecuting the criminal.
In most of these cases, you won’t need a visa if you are just in transit. For example, Chinese nationals don’t need a visa to go through the Amsterdam airport, but if they want to enter the city, they will need to obtain it.
Similar to this case, there is also a transit without a visa or TWOV in China. However, in order to be able to stay in China without a visa in transit, you need to already have a booked flight. Visa-free transit depends on the city, so while visa-free transit for 144 hours is available in Beijing, Tianjin and Hebei, visa-free transit for 72 hours and 24 hours is available in other cities.
The international zones have various rules depending on the country. It is quite common that while you are in transit, you are not allowed to leave the airport.
On the other hand, there are countries that issue a visa even if it’s only for transit. Russia is one of them. For travellers that are entering Russia by road or rail, the transit visa is issued for 10 days, and in case they are entering by air, the visa is valid for 3 days. In cases like these, you need to pay attention to not stay longer in the country since the border officials will bring you in for questioning and in extreme cases, you may even face a fine.
Another country that issues transit visas is the UK. Direct Airside Transit visa (DATV) is a visa issued for travellers that are from outside the European Economic Area (EEA) and Switzerland and they are changing flights in the UK. This visa is mandatory and you can check the requirements and whether you need it here.
More interesting examples of the international zones you can find in the video below:
Thank you for reading.