When you walk around in Seoul, it can all of a sudden start to smell like dog poo. Precisly that smell of when you got it under your shoe as little. But it isn't dog poo it is fallen fruit, from the maiden hair tree, that have been chrushed. This fruit is called Ginkgo and should be healthy for you. Like everything in Korea, but I dont know when the old ladies collect it by the side of the highway. They are a size of a strawberry.
I recognize the maiden trees leaves from asian paintings, you can find these trees far back in the history because it was a good source for food and medicine.
The fruit is pickeld or you can make liquor out of them. It's said they should be tasty. But the smell is horrible! Where I lived before it was a long avenue with only those trees. I almost kept my breath the whole distance.
So if you wonder what's that smell, don't look under your shoe look up in the trees instead!