ITAEWON town is long known for foreigner's street in Korea. There is history about this town.
After Korean war, US Army had been stationed at Yongsan. Korea was ruined by war and there was not many place for young US soldiers to enjoy.
US Soldiers want to enjoy, and poor Korean want to earn money. Naturally a marketplace formed to exchange money and entertainment. Koreanized western style bar, club, casino, and restaurant started their business. Also pawn shop for bankrupted soldiers, black market to distribute tax-free army materials.
It was almost the only place English is spoken. Unlike other parts of Korea, it was very natural to stay with foreigners. Not only soldiers but also other foreigners beginned to gather this area. Very unique culture was developed.
This is all pre-historic stories. Now Korea is developed country. There are a lot more decent place to have fun at Seoul. You can see foreigners at any place in Seoul. And US army has moved to other city. But Itaewon still have the heritage. You can feel cultural diversity in this area.
You can try Italian, French, Japanese, American dish at any part of Seoul. But you can not see Nigerian, Egyptian, Greek, Thainese, Brazilian, Scandinavian food except at Itaewon.
Itaewon is almost the middle of Seoul City. If you stay at Gangnam or near by city hall, you can visit here by taxi at lower than 10$.