For us Brits the most known obelisk has to be "Cleopatra's Needle" in London.
Obelisks can be found outside of temples, usually in pairs, and are used as guides for worshippers. Before pillaging the obelisk would have had a pure gold tip, this would reflect the sunlight and be visible for miles - a light house for worshippers.
Obelisks are engraved with Hieroglyphics telling the story of the deity whose temple they marked.