At the U1 underground station, on the western side, the sidewalk is covered by a roof that is held up by red iron poles. There are always two poles adjacent to each other, a big one and a small one. between those poles you can place and lock your hand so you can climb up.
Once you are at the roof, you can grab the side with both arms and move towards another pair of poles. there which you can them climb down.
When one is experienced in crack climbing, it should not pose a challenge.
There are not too many security cameras at the station, and staying out of their sight to not attract attention from security personell is not that bad of an idea.
Altough the crack is not difficult to climb an inexperienced crack climber might have to consider bringing a crashpad