At some point of the game it will start to rain. You need to go to the basement and grab a picture of the tower which is on the canvas with a triangle in the center.
Go outside, close to the telephone you will see a shinny spot with a triangle, stand on it (a white triangle will appear in the bottom right corner if you are on the right position), insert the picture of the tower in the glasses and use it on the big eye in the sky to get the achievement.