Cab: Say exactly: "Jong-ja Yok kai-yo" this will take you to the Subway station itself.
From ths station you need to cross the river. Once across the river turn right and head south, and walk until the second intersection with lights. You must walk until the second bridge ( the bridges are the only inter sections with lights). At the second bridge turn left going slightly up hill. Stay on the left hand side of the road, and there will be a convention centre and church on the opposite side of the street from you. At the first left turn you will encounter take it and walk in two streets. Turn right on the second street and about 50m up this street is the Topoban sign. It's on the right hand side of the street. The gym is in the basement. Check out my pics to have a better idea of what to look for.