@Lameme,
There's a total of 4 int. The first one is in the middle, then you walk 25 mts to get to the second, then 25 mts. to get to the third, then 25 to the fourth and finally 25 to a wall or something.
If I, in my map and starting in the center, walk 25mts to the second int., 25 to the third, 25 to the fourth and then the last 25, I get to a wall whatever passageway I take. It's like too perfect, the numbers are weird too.