A collection of Klein bottles
By welding together classical Klein bottles complex Klein surfaces can be built. Below you can see Double Klein Bottle, which also look like hourglass, and also Triple Klein Bottle with form of triangle.
These images were found at http://www.kleinbottle.com/double_and_triple_Klein_Bottles.html.
Alan Bennett created a recursive verision of Klein Bottle for the Science Museum in London. It consists of three Klein bottles, one inside another.
Most often, three-dimensional model of Klein bottles are created from glass. This kind of model allow to see the bottle as a whole. Bathsheba Grossman created a model using 3D printing technology. To make the model observable she cut through it hexagonal holes.
The image was found at http://www.shapeways.com/product/4KM9MDWCH/klein-bottle.