Sydney Metro(Subway) system - How I felt as Korean

 In Korea, all subways have only single floor. I can't explain how convenient and good for sightseeing those three floor subways are. 1st and 3rd floor are passenger seat and 2nd floor is opening door floor.

I wish those 3 floor subway system can be implemented to Seoul Metro system.
However, I found some negative factors about Sydney metro system.
The price of the subway ticket was too expensive. In Korea, we pay about a dollar on one way ticket. Even we go as far as another city(from Seoul to Incheon),  we at best pay about 3 dollars. But, in Sydney, I payed about 13 Australian dollar in just from Sydney International airport to Sydney Opera house which is not a long distance.