I only had 48 hours and only a physical card. When I arrived at the airport, the exchange store was already closed. The next day, I had to take a bus back to the airport to pick it up, and I also applied for SES. In 48 hours (three days), I visited N Seoul Tower, Hanboknam Bukchon Hanok Village Store, Sea Life Coex Aquarium, and Lotte World. Although I went to Lotte World on a Friday, it was still very crowded. It took 1.5 hours to queue for just one ride, which was incredibly frustrating. I later found out that Korean children were on winter break. I highly recommend visiting Sea Life Coex Aquarium; it takes about 1.5-2 hours. I had originally planned to visit Seoul Sky Observatory, but when I got there, I found out the tickets were only 10% off. I had researched it and then put it aside, not checking again before my trip, so I had to give up on that attraction and went to Lotte Mart instead.