http://www.nss.org/settlement/space/oneillinterior.htm
Gerard K. O'Neill created the O'Neill Cylinder in his book "The High Frontier". An O'Neill Cylinder consists of two cylinders which counter-rotate around each other, each one has a two mile (3 kilometer) radius, and a 20 mile (30 kilometer) length. The two cylinders counter-rotate to create simulated gravity by centripetal force: everything is pushed to the outer wall due to that force. However, some design choices stem from this, some to combat the negative effects, and others to take advantage the centripetal force. Due to the nature of artificial gravity, many people might experience nausea and dizziness. To combat this, the speed of rotation would need to be decreased to about two revolutions per minute. To take advantage of artificial gravity, different parts of the O'Neill Cylinder can rotate at different speeds. In the middle of the cylinder, the artificial gravity will be smaller than everywhere else in the cylinder, and manufacturing facilities would be placed here to take advantage of that fact.
The cylinders themselves would have six sections on them, half of them are windows, the other half is the ground. Behind each window would be a mirror so they could direct the sunlight into the cylinder, while night could be simulated by simply moving the mirrors to reveal the blackness of space. Day would be simulated as the sun moved across the mirrors, which would redirect the light. A side effect of the light being shone through the windows and reflected on the mirrors, would be that the light would be polarized, which could affect certain types of animals, such as bees.