−3°C Outside, 25°C Inside! You Can Build a Whole Seoul Winter Day Indoors—The National Museum Is Free and Open Until 9 pm on Wednesdays and Saturdays, the Aquarium Is 35,000 Won, the Observation Deck 33,000, the Jjimjilbang 14,000, and Here Is How to Chain Them on a Cold-Wave Day

Seoul in December averages 0.2°C, with mornings below −5°C. But indoors it is 25°C on ondol floor heating, and the trick for a Seoul winter is to turn that gap to your advantage and build a day that never leaves a building.

Better still, the indoor highlights come in a neat mix of free and paid. The National Museum of Korea and Starfield Library are free; the aquarium, observation deck and theme park are paid; and the jjimjilbang that closes the day costs a bit over 10,000 won.

The key is chaining only places that connect to a station or sit a few minutes from one. Yongsan, Gangnam and Jamsil link by subway, so the only ground you cover is from the station exit to the door.

This guide lines up each venue’s prices and hours from the official sites and lays out a free route and a paid route for the day. When a cold-wave forecast lands, just follow the order here!

A Whole Day for Free! The National Museum Until 9 pm on Wednesdays and Saturdays, Starfield Library Until 10 pm

✔ National Museum of Korea: permanent galleries free, 9:30 to 21:00 on Wednesdays and Saturdays
The most useful free place in a Seoul winter is the National Museum of Korea in Yongsan. The permanent galleries are free for everyone, open 9:30 to 17:30 (last entry 17:00) on Monday, Tuesday, Thursday, Friday and Sunday, and 9:30 to 21:00 (last entry 20:30) on Wednesday and Saturday. In 2026 it closes on January 1 and Lunar New Year (February 17), plus a scheduled gallery closure on Monday, December 7. An underground passage links it directly to Ichon Station (Line 4 and Gyeongui-Jungang Line), so you never walk outside.

With 7 halls, 39 rooms and 9,884 objects on display, a full day is not enough, let alone half of one. What makes it good in winter is how many rooms, like the calligraphy and painting galleries on the second floor and the ceramics on the third, are meant to be viewed sitting down. There is a cafe and a restaurant inside, so lunch does not require going out either. At Google 4.7 (29,146 reviews as of 2026-09-17), it is the top-rated indoor venue in Seoul.

The other free stop is Starfield Library on B1 of Starfield COEX Mall in Gangnam. The atrium library famous for its 13 m bookshelves is open 10:30 to 22:00, free of charge. Seats go first come, first served, and nobody minds if you sit there just to warm up without reading. Google 4.6 (6,934 reviews).

Seoul winter indoor venues: prices and hours (official sites, as of September 17, 2026)

Venue	Adult price	Hours and notes
National Museum of Korea (Yongsan)	Free (permanent galleries)	9:30 to 17:30 Mon, Tue, Thu, Fri, Sun; 9:30 to 21:00 Wed, Sat. Closed Jan 1; gallery closure Dec 7
Starfield Library (COEX)	Free	10:30 to 22:00. Connected to Samseong Station
SEA LIFE COEX Aquarium	35,000 won list	10:00 to 20:00. Up to 20% off online; two-adult ticket 51,000
Seoul Sky (Jamsil)	33,000 won	10:30 to 22:00. Aquarium bundle 62,000
Lotte World Adventure	Day pass 67,000 / After4 55,000	Indoor theme park. Folk Museum included
Sparex (Dongdaemun)	Day 14,000 / night 16,000	Night rate allows staying until morning

✔ Seoul Sky is not the only deck in town For more night-view options, the 『Seoul observation decks guide』 compares free viewpoints with paid decks, so an evening away from Jamsil can stay indoors too.

One Building Eats the Whole Afternoon! The 35,000-Won Aquarium and the Underground Mall at COEX

✔ SEA LIFE COEX Aquarium: 35,000 won list price, up to 20% off online
In the same building as Starfield Library is SEA LIFE COEX Aquarium. It opens 10:00 to 20:00 (last entry 19:00), and the adult list price is 35,000 won (70,000 for two adults). Booking online on the official site takes up to 20% off, and the two-adult couple ticket is 51,000 won online. Under 36 months enter free. Google 4.4 (12,144 reviews).

The easy order is library, then aquarium, then the underground mall. Warm up and sit at Starfield Library, spend an hour and a half in the aquarium, and finish with dinner inside COEX Mall. The whole sequence runs from Samseong Station (Lines 2 and 9, connected to COEX) without a single step outdoors.

COEX is also a convention center, so the exhibition side gets crowded at weekends, but the mall and aquarium flow is separate. On a weekday afternoon the aquarium is quiet; families only pick up during the school winter break from late December. If crowds worry you, aim for a weekday in early to mid-December.

Jamsil Is Three in One Building! Lotte World for 67,000 Won, Seoul Sky for 33,000, and Even the Night View Indoors

✔ Seoul Sky: 33,000 won, 10:30 to 22:00. Bundled with the aquarium, 62,000
Lotte World Tower in Jamsil is the ultimate weapon for indoor sightseeing in winter. Seoul Sky, the 500 m observation deck, costs 33,000 won for adults (13 and over), opens 10:30 to 22:00, and a bundle with Lotte World Aquarium is 62,000 won. Google 4.6 (6,534 reviews). With sunset at 5:23 pm in December, going up at 4:30 gets you both dusk and the night view.

Lotte World Adventure on the same grounds comes into its own in winter as an indoor theme park. The day pass (combined ticket) is 67,000 won for adults, and the After4 ticket for entry after 4 pm is 55,000 won, with the Folk Museum included. Its Google score of 4.3 (52,792 reviews) is not the highest, but the review count is among the largest of any Seoul venue, and short winter weekday queues are a real advantage.

At Jamsil Station (Lines 2 and 8), the mall, the tower and the theme park are all linked underground. Seoul Sky for the night view alone, Adventure for a full day, the aquarium bundle for families: pick one to match your budget, and the only outside air you meet is at the station exit.

Close With a 14,000-Won Jjimjilbang! Add the Underground Malls and Keep the Entire Cold-Wave Day Indoors

✔ Sparex in Dongdaemun: 14,000 won by day, 16,000 at night
The best way to end an indoor day is a jjimjilbang, the Korean sauna. Sparex in Dongdaemun is 14,000 won by day and 16,000 at night, and the night rate lets you stay in the sleeping room until morning. Know where the naked zone ends and the pajama zone begins and a first visit is painless. The hotter the sauna rooms, the more welcome they feel on a −5°C day.

Between stops, the underground malls earn their keep. The Gangnam Station underground shopping center and GOTO Mall at Express Bus Terminal connect straight to the subway gates, so shopping and meals never require surfacing. If your hotel is on the Gangnam side, use these two as your cold-day corridors.

There is only one caution for an indoor day: heating dries the air, so keep drinking water and moisturizing. The museum and the aquarium both have cafes, so sit down for water once every two hours. That alone changes how tired you feel by evening.

Two Routes for a Cold-Wave Day! A Free Route and a Paid Route, Map and Recap

To recap, a Seoul winter day works by chaining the Yongsan museum, COEX in Gangnam, the Jamsil tower and a jjimjilbang by subway, with the only walking between station and building. Two routes by budget follow. Ratings are Google Maps as of September 17, 2026; prices are from each official site.

• Free route (meals only): National Museum of Korea (from 9:30, until 9 pm on Wednesdays and Saturdays), then Ichon Station to Samseong Station, then Starfield Library (until 22:00), then dinner in COEX Mall
• Paid route (about 100,000 won): National Museum of Korea (free), then COEX Aquarium (online booking discounts the 35,000-won list price), then Jamsil, then Seoul Sky (33,000 won, go up at 4:30 for dusk and night view), then Sparex (16,000 won at night)
• Family route: a Lotte World Adventure day pass (67,000 won) is the whole day. After 4 pm, the After4 ticket is 55,000 won

• National Museum of Korea — Google 4.7 (29,146 reviews), 137 Seobinggo-ro, Yongsan-gu, connected to Ichon Station (Line 4, Gyeongui-Jungang Line), 9:30 to 17:30 Mon, Tue, Thu, Fri, Sun and 9:30 to 21:00 Wed, Sat, permanent galleries free
• Starfield Library — Google 4.6 (6,934 reviews), B1 Starfield COEX Mall, 513 Yeongdong-daero, Gangnam-gu, connected to Samseong Station, 10:30 to 22:00, free
• SEA LIFE COEX Aquarium — Google 4.4 (12,144 reviews), same building, 10:00 to 20:00, 35,000 won list price (up to 20% off online)
• Seoul Sky — Google 4.6 (6,534 reviews), 300 Olympic-ro, Songpa-gu, connected to Jamsil Station, 10:30 to 22:00, 33,000 won

FAQ

Are there free indoor places in Seoul in winter?

Yes: the National Museum of Korea (permanent galleries free, 9:30 to 17:30 Mon, Tue, Thu, Fri and Sun, 9:30 to 21:00 Wed and Sat) and Starfield Library at COEX (10:30 to 22:00, free). Both connect directly to a subway station.

How much is the COEX aquarium?

The adult list price is 35,000 won, with up to 20% off when you book online on the official site. The two-adult couple ticket is 51,000 won online. Hours are 10:00 to 20:00, last entry 19:00.

What are Seoul Sky’s price and hours?

33,000 won for adults (13 and over), open 10:30 to 22:00. A bundle with Lotte World Aquarium is 62,000 won.

Is Lotte World worth it in winter?

It is an indoor theme park, so winter suits it. The day pass is 67,000 won for adults and the After4 ticket for entry after 4 pm is 55,000 won, with the Folk Museum included.

Can I get between these places without walking outside?

The National Museum connects to Ichon Station, Starfield Library and the aquarium to Samseong Station, and Seoul Sky and Lotte World to Jamsil Station. Chain them by subway and the only outdoor walking is from the exit to the building.