Nami Island is a great day trip from Seoul and is easily accessible via subway. It is located in/nearby Chuncheon and is on the teal subway line and ITX.
I was probably not as awestruck as most of the other visitors because I don't really watch Korean dramas. After my visit, though, I felt compelled to watch "Winter Sonata" and it was a pretty good drama for an introduction to K-Dramas. The soundtrack is especially nice.
Even though I did not know the drama, I very much enjoyed the scenery, fresh air, and the views from the island.
Basically, the island is a tribute to the drama and all of the attractions are major points of various plot elements in the drama (see below).
I am not sure which season is best to visit Nami Island. The winter tour fits the drama scenes more, so if you're a major fan of the drama, you will definitely enjoy this trip.
There are concrete snowmen all around the island and they look more appropriate with a dusting of snow on the ground than with temperatures in the upper-30s Celsius.
Your trip starts via a ferry boat, but you can choose alternate "adventure" transportation if you so choose (ie. zipline or a crazy jet ski thing). You then have to go through "Immigration," since this ferry ride has transported you to another kingdom. You can get a kingdom passport, if you wish.
Once you're on the island, you have only a few restaurant options. I went to the Country Restaurant (post includes menu translation) during my summer visit and would recommend it. It has more homestyle food and serves dongdongju (Korean traditional alcohol) and is relatively cheap.
Apart from the very tourist-y feel and all the drama references, Nami Island is really beautiful and is a great break from Seoul life. Even if you're not into the drama, I would recommend checking it out for the fresh air and beautiful scenery.
I have more pictures from my summer visit that I will post later. The scenery is much better in summer, when there are leaves on the tree and the water and sky are blue.
I guess I would recommend visiting in the summer or autumn if you can. I just feel like sightseeing is a little more enjoyable in the warmth.
It is a very popular dating course in Korea, so if you get a little turned around on the subway, just alight at the stop where all the young Korean couples do. But, if you miss that stop, you can just decide to do a day trip in the city of Chuncheon instead.
From Sangbong Station take the Gyeongchun (teal) Line to Gapyeong Station (14 stops), about 1 hour 15 minutes.
From Gapyeong Station, take the 33-5 bus to the Nami Island stop.
From Yongsan Station, take the ITX towards Chuncheon. Alight at Gapyeong Station.
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If you are traveling to Korea, while English is often available on signs and at tourist destinations, it may be wise to know a few phrases since oftentimes the staff at restaurants and other tourist destinations, bus stations, do not know English well. I have looked over multiple Korean phrasebooks and I recommend the Lonely Planet Korean Phrasebook & Dictionary for its small size (makes it great to carry around) and its ease of use.
It gives you a feel of all the different neighborhoods and districts of Seoul and a brief overview of what each district is known and how the city is laid out to help you plan the most efficient and fun trip!
I definitely recommend, if you get the chance, to get out of Seoul and really explore Korea. Each province and city has its own feel and personality. Plus, the country is about the size of Indiana and transportation options abound, so traveling around is definitely do-able.
Choosing the best country guide was a little more difficult for me. I am typically a Lonely Planet fan, but I found their guide to not be quite as current as this Frommer's guide.
Having an up-to-date guide is very important in Korea since things can literally change overnight!