That's okay, it's understandable. So you have been in Seoul with many other tourists.
But this little river is a famous spot for tourists as well since last year. (It wasn't built before then.)
And right in the middle of downtown near the City Hall. You must have passed the water beneath your car.
And don't worry if you are not fluent in Korean. It will be not that hard and I may be able to help you more.
