(This post is in response to Annick's questions, thank you for the idea.)

When you arrive in Incheon airport it's super easy to just hop on the subway with your bike, however that is not the case in Busan.  Gimhae airport is located just West of Busan city and it is connected to Busan by a light railway train. It is an automatic elevated train and no bicycles are allowed on it. 

So how to get from Gimhae airport into Busan? Or how to get from Gimhae airport to the Nakdong river path leading to Seoul? Or how to get from Busan to Jeju by plane? Well of course you can take a taxi, if the driver agrees and if you take your wheels off. Some airport buses would probably let you store your bicycle under the bus in the luggage department. 

But the best option yet is to simply ride your bike. 

Few people are aware that the airport is 1,5km away from the Nakdong river bike path. So with a little GPS and Google or Naver maps it should be super easy to navigate yourself to the bike path. 

Once you are on the path you can cycle down the West bank all the way to the first certification center, it's about 10km.  If you happen to be doing that in the last week of March or the first week of April you will cycle through a 10km tunnel of Cherry blossom heaven on a dedicated bicycle path. ​

Near the end of the lane of trees the path will turn to cross the river and you will soon see a sign for the certification center. After the certification center you can cross the rest of the river and start the route on the East bank of the Nakdong river and head to Seoul. Or you can cross the bridge and go straight for 1 km to reach Hadan subway station. From Hadan you can take the subway to anywhere in Busan. 

If you cycled from Seoul, ended in Busan and want to take a plane to Jeju, you can cycle from the certification center to the airport.

Routes: 

• Gimhae airport to the Nakdong river Certification center
• Gimhae airport to Hadan subway station

Distances:

• 10 to 13 km one way.

Road surface:

• 90% cycle track
• 10% car roads

Elevation:

• Flat with small ramps when you leave the bicycle paths to enter the road. 

Tips:

• Always cycle on the East bank of the Nakdong river to and from Seoul if you want an easy path to follow. Cycle on the West bank if you want more challenging hills and navigation. 
• The West bank of the river always have less people, so for cherry blossom time, Saturdays or holidays that's the best place to cycle just for a day trip.

Bicycles on an airplane

• At Gimhae airport you can pay and they will provide a box for your bike and pack your bike in the box for you. But you will have to disassemble your bike by yourself. 

It has been my goal to cycle alongside the Taewha river in Ulsan and to explore all the nooks and cranies with my bike in Ulsan Grand Park for a long time. Finally with the help of the slow train I managed to explore these lovely places.

Every Saturday at 7:38am a train leaves from Haeundae station and travels all the way to Gyeongju. This train departs from the brand new Haeundae station in the middle of nowhere, not close to the subway or the ocean or nothing. Actually the closest thing to the new station of note is the big highway running nearby. But if you use your pedals and wheels it's not hard to get to the new station. 

And so only once or twice a day the slow train includes a cafeteria car, which also contains 5 bicycle racks and lots of space to stack or keep more bikes. On the Korail app you can book the bicycle seats if you use the app in Korean and if the seats have not been sold out. ​

Even though the train did not have any bicycle seats left when I booked, I just put my bike in car 4, its the cafeteria car so there's lots of space.  The train is a really great way to get to and from Ulsan or Gyeongju without a 60 or more km ride. ​

From Haeundae station to Taewhagang station it takes just under 1 hour. Then from the station you can cycle right away to the river and the cycle track, it's just a few hundred meters. There are two courses, one going West and one going North. I tried the western course and left North for another day. 

The Taewha river is not so different from many other river paths in Korea, but riding along an unknown road was refreshing and relaxing. Compared to the Nakdong river near Busan there were also very few people or cyclists around, so you could really just spin and cruise ahead on the generally flat course.  Just as you set into your rhythm and think it's going to stay the same, you are delightfully surprised by bamboo forests filling the banks of the river and lining the cycling path.  It feels like being transported to Korea's Bamboo tourist destination in Damyang, except that you can actually cycle through these forests. A truly wonderful experience. 

Once you reach the furthest Western point of the cycle route, staying on one side of river you find a welcome and neat little coffee shop with sandwhiches, drip coffee and more. After grabbing a cup and a bit to eat I set off back along the river on the other side.  At 3pm I took the train back to Haeundae, but I will be back to finish the Northern cycle track. 

Route: West - East Taehwa river cycle path (Ulsan)
Distance: +/- 30 km
Terrain: Cycle track
Elevation: Flat
​Start: Taewha train station (Ulsan)

The Seomjin river in the Southern part of Korea is not one of the main four river cycle paths. It will not help you earn a cross country or grand slam medal and it does not connect or go through any well-known places. 

But what this river lacks in credentials, it makes up for by being one of the most beautiful and pleasant cycle routes in Korea.  The Seomjin river runs past the Gurye mountains and through the fruit orchards of Korea. Instead of the endless flat and monotonous views of the Nakdong river, you are rewarded by tree-lined lanes ready to burst into their autumn colours and winding paths against the shoulders of the surrounding mountains.  Even the river itself is filled by interesting rock formations and seem wilder and more untouched. 

Sadly I found it hard to capture the beauty of the route with my camera while cycling, I just drank it in along the way and now and then took a picture, which still failed to capture it's true essence.  Like any cycle trip during Chuseok the late summer weather was perfect, with flowers, insects, lots and lots of spiders and more heron's than I could care to count.  The lack of other cyclists was also refreshing, 90% of the time we had the path to ourselves. 

As for accessibility, the Seomjin path is as flat as it gets, with not a single hill of worth to mention. And yet it's twists and turns and short ups and downs with the ever changing scenery keep it interesting and enjoyable.  We barely ever opened a map or looked at our phones, as the path is very well marked with every twist and turn. Every certification center had ink and stamps (and a few spiders).  We also forgot our cycling passports at home, so simply bought new ones at the Southern starting point of the route. 

The beauty of this river is also that anyone can do it in a weekend. Just take a bus to the start on Friday night. Cycle 80 to 90km on Saturday, cycle 60 to 70km on Sunday and take a bus back Sunday late afternoon.  I am already thinking of when I can come back for a weekend to do it again if I had the chance. 

Wheel pressure check, lights check, batteries check, patch kits and extra tubes check. We are out the door and on our way. While most of the cycling community will be trying to complete Seoul to Busan we will be heading to hopefully less crowded paths.

The beauty of this moment, sitting in the bus to Gwangyang is the unknown. The only surety is our bus tickets from Busan to Gwangyang and back from Mokpo to Busan. Tonight's accommodation, tomorrow's lunch and the cycle path are all wonderfully unknown and exciting!

Start: Haeundae
Finish: Gijang and back to Haeundae
Distance: +/-40km
Elevation: mostly flat with a steep hill on Dalmaji road
Road surface: mostly car road, a small section of cycling track. 
Transportation: Take the subway to Jungdong station on the green line, Exit 7
Transportation back: There is an option of a train between 15:00 and 16:00 from Gijang or any other East coast station back to Haeundae or Dongnae station. It has 5 bicycle seats. 

After a bit of a lull in my cycling I'm back and I've been out and about lately revisiting some favourite routes. A lot of construction has been going on near Songjeong beach and Gijang, due to the development of the East Coast Tourism Complex. A huge Lotte mall has been built and they are still busy building a theme park, water park, hotels, retirement villages and golf courses.  Some of this construction is resulting in new roads, tunnels and routes that did not exist before. 

I've also been noticing the signs going up for the new East coast cycle route, starting at the top of the East coast of Korea. It seems down here near Busan, they are simply adding signs for the route and not really creating any new cycling roads. Also some of the route seems to follow the busy road 14, while there are other lovely coastal alternatives available.  I was really hoping the old train track would be converted into a cycling track going round Dalmaji, but it will be left as an old train track for tourists to walk on, while Dalmaji hill has become part of the East coast cycling route. I guess for the long distance cyclists it will become that last climb before descending into Busan and Haeundae.

Another change is that Dalmaji road has been re-paved, almost 100%. This is great news! It's been part of my commute in the past and now many of those nasty potholes and uneven bits are history! There's also some markers installed near drain covers that stand out, which is a nice touch.

Above is the route I would recommend for the first 30 km up the coast. There are subtle changes. 

• Descending from Dalmaji, turn immediately right and go straight over the old train line to Songjeong beach.
• From the end of Songjeong past Lotte mall up to Jukdo coastal town has a dedicated cycling lane.
• There are two new connecting roads and a cycle friendly tunnel between the coast and road 14 just after Lotte mall and before Jukdo coastal town. (However I would just try to avoid road 14 if possible.)
• For a fast finish and a loop ride, you can cycle up the coast to Gijang and then just take road 14 back. Just be aware it will have traffic and buses.

A lovely 50km flat ride along the river and you can take a train from Miryang back to Busan at 18:20 with a bicycle rack. 

I've cycled up the Nakdong river many times, but this time I decided to veer off the dedicated cycled route and try to make my own way to the town of Miryang. However to my great surprise I found a dedicated cycling path all the way to Miryang. What was even more surprising is that this path is not even indicated on Naver maps, it's completely empty of other people and all between the farmlands. This was literally the perfect 50km if you just want to cruise along with the wind in your hair or try to reach top speeds.  ( I chose to cruise.)

Of course you can cycle to Miryang and back for a perfect 100 km.

Start: Yangsan
End: Miryang
Distance: 50km
Elevation: very flat
Surface: cycling road all the way
Transport to Yangsan: Take the subway to Yangsan station or take a bus to Yangsan
Transport from Miryang: Take a train to Busan station (18:20 only train with cycle racks) or take a bus to Sasang.

One of my favourite rides in Busan, is from Haeundae up the East coast in the direction of Ulsan.  Scroll down for some pictures and a detailed google map of the route.
DISTANCE: 85 - 95km