I was asked to map the rooftops in Seoul you can go up to without paying. There were two conditions: include only places the public can actually get into, and if paid observation decks are mixed in, keep them clearly separate from the free ones. The first upload had 39 places. Now there are 90.
From 39 to 90 in five rounds
It started at 39 and grew to 45, then 50, as places were confirmed. Up to that point, all of them were free, open rooftops and gardens. Next, 10 paid observation decks, like Lotte World Tower's Seoul Sky, N Seoul Tower, the Seoul Dal balloon and 63 Square, were added on top as a separate group, making 60. Finally, 30 were merged in at once, making 90. They span 24 districts. Jung-gu (15) and Jongno-gu (13) have the most, and only Gwanak-gu doesn't have a single one yet. 78 of them you can go up for free.
As soon as paid decks were mixed in, the map got confusing
With paid decks added to a map of free rooftops, you couldn't tell them apart from the pins alone. So paid decks get their own glowing amber pin, a fee badge on the card, and a separate notice banner above the list. The filter chips have their own entry for paid decks too. Fees are written exactly as posted, like "Adults ₩31,000 / Children ₩27,000," not rounded or blurred into "₩20,000–30,000 range."
First, the fake comments came out
Early on, the visiting-tips area was filled with mock comments. I stripped them all out and hooked up Supabase so only tips people actually left would show. It works with an anonymous session and no login, input is HTML-escaped, and there's a rate limit to stop spam. I also added a form where people can report rooftops that aren't listed yet. Once I forgot to add the Supabase script tag to index.html, and the comments disappeared entirely. The fix was one line.
While renaming it, I fixed the broken map too
The name changed from "Seoul Rooftop Map" to "Seoul Sky." It was the right name when there were only rooftop gardens, but it stopped fitting once paid decks came in. Along with the rename, I added filters to the map legend and fixed the background map, which until then hadn't been loading at all. The map is drawn with Leaflet.
Four languages, and subway stations
At first there were two languages, Korean and English. All 90 places got separate English names, addresses, opening hours, fees and view descriptions; later Chinese and Japanese were added, for four languages. All 90 are filled in for all four. The chosen language is remembered in the browser, so it stays when you come back. Added at the same time was the nearest subway station, which only 85 places have. The other five, like the Eunpyeong History Hanok Museum, the Peace Culture Bunker, the Songpa Book Museum, the Bangbae Forest Environment Library and the Wolgye Library, are awkward to walk to from any station, so rather than force an answer, I left them blank.
Not every rooftop was a rooftop
Once they were all gathered, they were so different in character that they couldn't be lumped together. Now they're split into eight types: public facilities (24), parks and sky gardens (21), department stores and malls (21), landmark observation decks (11), park and mountain skywalk decks (5), mountaintop lookouts (4), ordinary building rooftops (3), and an art museum (1). Of these, four, Somangtap on Umyeonsan, Malbawi on Bugaksan, the Buramsan elevator and the Maebongsan pavilion, aren't strictly rooftops. They still meet the standard of "a point where you look down over Seoul," so they're in, but their type is marked separately so you can filter them out.
How to use it
Pin icons show the type: garden, café, open at night, paid deck, viewpoint, building. The filter chips at the top let you narrow down to All, Gardens, Cafés, Open at night, Free, Paid or Open access in one tap. There are three access statuses. 78 places you can just go up to with no reservation or conditions, and 11 have opening hours, advance booking or a tour requirement. The last one is the rooftop observation deck at the Sejong Center for the Performing Arts, scheduled to open to the public sometime in 2026, so its fee is still listed as "TBD." For height, Lotte World Tower's Seoul Sky is the highest at 500 m, and among the free ones, the Somangtap lookout on Umyeonsan is the highest at 293 m.