Making the Bupyeong Underground Map: From a Guestbook Post to a Board in 42 Hours

September 7, 2026

At 15:33 on 10 July 2026 a guestbook post asked for a Bupyeong underground mall map. First commit at 19:49 the same day; 42 hours later the reply went up: it is in, balance not guaranteed.

No such map existed in five catalogues. So it became an original rather than a recreation. Machine rooms are impassable walls, stairs are mountains, the Gyeongin railway is a river, exit numbers are towns.

Seven finished games in the two months since, all by Dutch, Japanese and German players: humans won 7 of 7, averaging 180 points. "Balance not guaranteed" turned out to be accurate.

One of the fourteen maps on this site is neither an official map nor someone else's fan map. It is the underground shopping mall under Bupyeong Station in Incheon. This is how it got here.

One line in the guestbook

On the afternoon of 10 July a suggestion appeared in the guestbook: please add a Bupyeong underground mall map. The operator answered within the hour. Does such a map exist? If so, send a link. If not, I will make one up.

First, the search. 174 Age of Steam expansions linked on BGG, 183 on the fan wiki, the map database, 58 in an open-source implementation, Korean forums. Zero. The research tool that ran the search advised holding off: with no original to reproduce, building one would be invention. Which was correct, so invention it was. In the map data the source field just says fan.

The Bupyeong Underground board. Mall sections are cities, exit numbers are towns, the Gyeongin railway runs across the south as a river — The Bupyeong Underground board. Five mall sections and three stations are cities, exit numbers are towns, and the blue line across the south is the Gyeongin railway.

Translating a mall into hexes

This game has four kinds of terrain: plain, river, mountain, and impassable. The mall had four things to match.

Real thing	On the board	Why
Machine rooms, parking cores	5 impassable hexes	The walls of the maze. Why first-timers get lost
Stairs and level changes	8 mountains	The bottlenecks between sections. Expensive to build through
The Gyeongin railway	12 river hexes in one southern row	Reaching Dongsu Station south of the tracks means crossing the river
Exits 1, 5, 9, 14, 18, 22, 26, 31	8 towns	Real exit numbers. Exit 9 sits in the middle of the Bupyeong Station, Daea and Sinbupyeong triangle
Five mall sections, three stations, the market, the culture street	9 cities	Bupyeong Station and Market Rotary are red-cube hubs with three cubes each

Drawing this by hand goes wrong. So a small generator was written: lay it out in screen coordinates, convert to hex coordinates, and check by machine for duplicate coordinates, connectivity with the walls removed, minimum distance between cities, and unique dice pairs. The check had one name: is the dungeon still passable.

Eight rows by eleven columns, 88 hexes. The same small class as the New England map (86), so it is a 2 to 3 player board with a 10-turn house rule for two. The rules are stock Rust Belt. Only the terrain is different.

Four hours sixteen minutes, then 42 hours

15:33 the suggestion, 16:32 the operator's reply.
19:49 first commit. Map validator passed, 2 and 3 player self-play finished on three seeds each, 108 tests green.
19:56 Korean place names for all nine cities and eight exits. City names had no translation layer then, so the Korean went straight into the data.
Released the following night. The next morning: it is in, balance not guaranteed.
Three weeks later, English names wired in, so overseas players read Bupyeong Stn. and Exit 9.

The update history at the bottom of the home page never mentioned this map. It went in quietly on the same day as an AI overhaul and a nickname merge. This article is its first official mention.

What seven finished games say

Measure	Value
Finished games	7 (six 3-player, one 2-player), 0 abandoned
Human win rate	7 of 7
Human average score	180 (162 to 207)
Average length	20 minutes
Countries	Netherlands 5, Japan 1, Germany 1

Finished games through 2026-09-07, operator excluded. Seven games: read the direction, not the digits.

Self-play already showed 2-player scores like 115 to 40, repeatedly: whoever grabs the Bupyeong Station hub first has the edge. Real games agree, with humans unbeaten at 180 points on average. The "balance not guaranteed" reply was honest. And not one Korean player has finished the Korean mall map yet, the person who asked for it included. Right now the Bupyeong underground is best known to Dutch players.

The real Bupyeong underground

The game is better connected than reality. The Market Rotary mall is not actually joined underground to the station mall; a connection was planned and dropped. On the board they are linked as cities. A few more facts.

Construction began in 1977 and the Sinbupyeong section opened in 1978. It was built as a civil-defence shelter and opened as a walkway in peacetime.
1,408 shops on 31,692 square metres as of 2014, certified by the Korea Record Institute and the World Record Academy as the most shops on a single underground floor. Often called a Guinness record. It is not one.
31 exits, 120,000 to 130,000 people a day, nicknamed the underground dungeon. Renamed Bupyeong Modoo Mall in 2016.
Bupyeong Station was one of the seven stations on the Gyeongin line when it opened in 1899, Korea's first railway. The line pulled the centre of Bupyeong south from the foot of the mountain to the station, and the mall grew beneath it. That is why the board draws the railway as a river.

Sources

This site's records: the guestbook post (2026-07-10), the map design notes and generator, commit history, finished-game logs
Kyunghyang Shinmun, 2014-11-07 (Korean), World Record Academy
Incheon Today: construction and civil-defence origin (Korean), Incheon Facilities Corporation (Korean), Wikipedia (ko): Bupyeong Modoo Mall
Wikipedia: Bupyeong Station

Play the Bupyeong map