This day I started early, because I wanted to see all the tourist attractions in one day. If someone tells me something is impossible it makes it so much more fun to try it anyway.
So I started by taking the MTR to City Hall (you should use exit 5) and then took (of course) a wrong turn, so that I was walking through the streets again and explored the Namdaemun market and also saw the Sungnyemun Gate.
There I realized my mistake and turned into the opposite direction again. So here is a simple tip: If you get out of exit 5 at City Hall station, trust your eyes and just follow them to the temple ahead of you. That is the right direction to Gyeongbokgung Palace.
Fortunately I still was able to see part of the Gate Guard Change and then enter the Palace to see the different buildings, gardens and the National Folk Museum of Korea, which is really interesting and very well designed!