Seoul boasts one of the most convenient subway system in the world.
It is safe and pleasant.
Most of all, you can easily visit almost all the major places in Seoul by using the subway.
Some foreigners worry that they might pay through the nose for taxi fare in Seoul.
But I can assure you that most of the taxi drivers in Seoul are kind and conscientious. There is a small chance of meeting an unconscientious taxi driver.
Nevertheless, if you are still uncomfortable with using taxi in Seoul, then, you should definitely consider using subway when you travel to Seoul.
Here I share some information on subway system of Seoul.
I bet you will find it very useful when you stay in Seoul.
You may also search, “Korea Travel Books” on Google Play store or Apple store.