When did you find out that Dongdaemun isn't actually in Dongdaemun-gu?

Source: Women's Generation (InTP Japchae)

The magnificent Heunginjimun (Dongdaemun) located in the heart of the city

This gate is not located in Dongdaemun-gu, Seoul

But in Jongno-gu

For real

Of course, Dongdaemun Station is also in Jongno-gu

Then what about DDP, the landmark of Dongdaemun?

Yes, that's in Jung-gu

But then again, the CI (Corporate Identity) of Dongdaemun-gu is Dongdaemun

What?

Source: https://cafe.daum.net/subdued20club/ReHf/5659727