Okay, Seoul.
I'll start with the cool landmarks & historical sites & stuff that's a must see, and move on to districts and experiences after that.
Full disclosure, I haven't been back to the Republic of Korea since COVID started so I don't know what has shutdown or been affected.

Start with Lotte Tower. It gives you an impeccable view of the city, there's a ton of stuff nearby, and the mall is phenomenal

Lotte World Tower

https://maps.app.goo.gl/QWnkKvWwW9spSv327

Gyeongbokgung Palace is beautiful. Make sure to take time to walk through the Gwanghwamun Gate so you can see all the statues. Inside the palace is the National Folk Museum. There are always young men and women there wearing hanbok for photoshoots, and they all look amazing

Gyeongbokgung Palace
+82 2-3700-3900 https://maps.app.goo.gl/AwxcexrVWiV3mP8R9

The War Memorial of Korea is super super cool & located near USAG Yongsan & Itaewon, where a ton of Americans and other ex-pats live, work, and party. https://maps.app.goo.gl/RehPqSRVyi9w2pL1A

Bukchon Hanok Village is between two palaces & features historical landmarks & architecture from 600 yrs ago. Also they have some BOMB coffee shops. You can walk there from Gyeonbokgung Palace. https://maps.app.goo.gl/F8wVRQvQse4n2MxZ6

Jogyesa Temple was built at the beginning of the Joseon Dynasty & has an enormous amount of religious, cultural, and historical significance. Try to visit next month for Buddha's birthday so you can see the festivals & things. https://maps.app.goo.gl/FEccThXo879CLAyp9

Namedaemun Market is the oldest in all of the Republic of Korea. There is nothing you cannot find. Fish, dumplings, hotteok, skincare, mink blankets, you name it.

https://maps.app.goo.gl/vxM4C7ZKvWeWMUiv6

Gwangjang Market is also fantastic! More food-based than anything else. It was featured on Netflix Street Foods and yes, those homemade noodles lived up to the hype. Get the ginger tea & kimchi dumplings too

https://maps.app.goo.gl/5tcv1Bo3XmKUfJpN9

Seoul Tower is a must. Try to hit it around dusk so you can see sunset across Seoul & then see the whole city light up in neon.
I recommend you take the cable car unless you have a few hours to hike up & down

Namsan Cable Car
https://maps.app.goo.gl/LWdMRuQ8vnMY5Kwt6

Get your ass to a baseball game at Jamsil Sports Complex, it's an incredibly good time.

https://maps.app.goo.gl/bbyPq98hAuY9kibs8

Cheongyecheon Stream runs through the city and is a beautiful nature walk where you can stop off for coffee or drinks along the way. Absolutely beautiful, regardless of season. I recommend you start at the Cheonggye Square, that whole area is cool af.

https://maps.app.goo.gl/79FzgPMP4zrWj8HX7

Hike the Bukhansan Mountain, sweat a ton, & see Seoul from a summit https://maps.app.goo.gl/vTFyW7mPUEr2dMip9

Inside the city, hike the City Wall trail that encircles what used to be the fortress grounds in the 14th century IIRC https://maps.app.goo.gl/HcdoEZWWYz5f5tGc7

Gangnam District is cool for shopping & eating & has a ton of cool art statues. Start at COEX Mall and wander outward from there. You really can't go wrong. https://maps.app.goo.gl/GPh5im2CS8osQqCu7

The Hongdae neighborhood (district?) Is full of arts, uni students, expats, and ample nightlife options. Come for the cute pop-up booths and stay for the soju bowls followed by Western style brunch in the morning.

Also the BLACKPINK house is here. https://maps.app.goo.gl/3terAExGkdVzEGWEA

Speaking of soju bowls & expats:

Mike's Cabin https://maps.app.goo.gl/K6zBcFc97hcjrk939

For street food, shopping, & cafes galore, you gotta go to Myeong-Dong. It's not optional. The Lush Store is 2 stories of excellence, the street food is indescribably good, the outdoor booths are diverse & amazing, and you can't swing a dead cat in that area without hitting

...a restaurant serving 5 star food.

Visit a cat cafe too, they're gimmicky but kinda neat. https://maps.app.goo.gl/rnecGMDdmRzz7X7j9

Myeong-Dong has so many skincare/beauty stores within walking distance of the main strip, on literally any budget. Innisfree, Aritaum, Nature Shop, Etude House, Laniege, Skinfood, you name it, they have it.
Do it.

Make SURE you buy yourself some hotteok & some fried milk.
Trust me.

Make sure to stop by Myeong-Dong's Artbox if you have anyone in your life obsessed with adorable stationary, hobbies, cute accessories, art supplies, etcetc. They also have a whole floor of candy & toys.

I cannot remember wtf this is called but there's a 2nd floor restaurant that overlooks the Myeong-Dong street food alley that has it. 10/10 they'll need to roll you out of there on a cart

This is going to be hotly contested, but the best Udon joint is inside the Yongsan Train Station. https://maps.app.goo.gl/uX6Jmp7JbbvuWWmZA

If you're jonesing for a western-style brunch buffet after a night out, you can't go wrong with Dragon Hill Lodge tbh.
So many options, and it's within walking distance of Itaewon https://maps.app.goo.gl/QnsAB4rR4NXE87rb6

I'm running out of steam and I'm convinced I've forgotten something, so feel free to chime in below & I'll add you to the thread

Frankly the city is so massive and each neighborhood/district is so dense that they probably need their own threads lol.

Have fun!

Gundam Base I'Park Mall
https://maps.app.goo.gl/xNw5o5oTwMCAo5uc9 https://twitter.com/kris_alexander/status/1385053466431672325?s=19

https://twitter.com/DesertStorm24ID/status/1385102881733455875?s=19