Korean culture has the concept of a "jjimjilbang” which is similar to a bathhouse in Japanese culture, with some key differences. It's a lot more... modern. We're talking a floor of arcade machines, snack areas, novelty saunas, and sleeping rooms. It's a great place to just hang out for a day.
We tried to get to the jjimjilbang (Dragon Hill Spa) but got hopelessly lost. Turns out "Seoul Station” and "Airport Transfer” were two stations mushed together, and you have to tag in and out. We walked in literal circles until we actually found a staff member (surprisingly rare in Korean public transport) that showed us where to go.
The REAL struggle is carrying the damn luggage up and down the stairs everywhere.
Ate food at the end of our ordeal since we were so hungry.

The book store in Yongsan station has an entire row for you to just sit and read.
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Once we got to the spa though, it was pretty awesome. The sleeping area was filled with people, and you scan your wrist band to pay for stuff. There was a sauna at 88 Celsius, and another at -22 Celsius! Both were pretty exciting to try for about 1 second.

Resting area. No beds, only floor!

Unheated room, no one was in it because it was like 0 degrees.

So you can see the types of saunas here. The left one is -22 degrees.

I braved the cold just for you so you can see it.

And this one was 88 degrees. Some SERIOUS heat going on here.

This particular one has you resting on... rock salt. For some reason. About 53 degrees I believe, so treat it like training to go to the Pilbara.

Nice and comfortable rock pillows and rock beds, Korean style comforts.

Gaming floor downstairs, you know, in case you wanted to frag some noobs after relaxing in the sauna.

There was a couple of pyramids with sleeping... holes in them, which muffle the sounds of the outside world.
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Next was our flight to Taipei, Taiwan, our next destination!
Only two inspection gates were open at the airport, so the lines were looooong. Because of this we were super late for the plane. We basically had to sprint all the way to the monorail transfer (which we made JUST in time), and sprint out of the train (someone stacked it up the escalators), and sprint all the way to the gate. Not a pleasant experience unfortunately. We came two hours before the flight too!
The flight itself was 2 hours long, which was a snap. Though we were covered in sweat and hyperventilating for a large chunk of that time.