The Metropolitan Subway of Seoul, South Korea, is one of the busiest in the world, with over 8 million trips every day. The system totals 755 km over the fourteen lines (compared to 214 km on the Paris MÃ©tro and 416 km on the London Underground.)
Signs on the Seoul metro are all written in Korean and English, and voice announcements are made in Korean, followed by English and in some cases Japanese and Chinese. This makes getting out at the right station, transferring onto the right train and getting out on the right side of the train that much easier for foreigners.
The Koreans pride themselves on having very low crime rates, although there are many gangster movies! You can leave your belongings on subway shelves without any concern, and children play safely in the streets at night.
Avoid kissing and caressing on public transport.