Da Nang is a small city in central Vietnam that is a very popular destination for Korean tourists (thus there are many cheap options for flights from Incheon). You'll get to experience tons of great food and coffee, as well as the lovely hospitality of the Vietnamese people. Nearby you'll find the ancient city of Hoi An, and the more modern citadel of Hue. Travelling on a US passport, you will need an electronic visa to visit so start planning early!