What is the name of the church in Seoul with the triangular facade?

You can see it from the highway when you take a bus from Osan to Seoul (it's on the left side of the road,) about 15 km north of Suwon. It has the archetypal spire and red neon cross, but where you would normally expect the gable over the nave to meet 90-degree walls, it just continues in a steep slope more or less all the way to the ground.