The South Korean island of Jeju (formerly Cheju) lies directly off the south coast. Jeju airlines had an incredible sale on fares. The two of us flew round trip for under 100 USD. We only had one day to explore so chose and interesting UNESCO heritage location and headed out by bus. The ride was interesting as it alternated between villages, the coast, and through farm areas. It was quite easy to get around even though the Maro Guesthouse was a little out of the way. Taxi driver called to get exact directions. We each have stored value Korean Travel cards. We use the same card all over Seoul, Busan, and on Jeju buses.
Here is a pictorial summary.