The container is hidden on the wall, near the original hide location in the pipe. You will find it easily by looking at the spoiler on my recent update. There is no pen inside. Please put it back carefully and make sure that it stays closed.
The area (nearby) is usually crowded so be careful to not be spotted, just look like you are admiring the view and taking photos.
You can start from the city center and walk up the stairs (forget about parking there on workdays), or go to the cache location by car, where you will probably find a parking spot nearby.