The movie Escape Plan (starring Stallone and Schwarzenegger) is about a man who's been testing federal prisons for their capacity to prevent an escape from their maximum security. He is then recruited by the CIA to test a certain underground prison facility.
In the movie, Breslin (Stallone) ends up creating a sextant to figure out where the prison was located. A sextant is an old astronomical tool used commonly in nautical navigation (celestial navigation). It is a tool used to measure the angular height/ altitude of a star with respect to the horizon. Seafarers had to be familiar with the night sky in order to put the sextant to use. First of all one must locate Polaris, the north star. A common misconception is that Polaris is a really bright star; this however is not true. Being familiar with the patterns of the constellations and knowing which is next to which can help. Of course it helps also if one has a compass to point you in the general direction.
The measured angular height of Polaris will give you the angle of your latitude. As an example, if we were to say that we measure Polaris to be ~13 degrees from the horizon in Manila then we can say that Manila is located at a latitude of 13 degrees.