Somewhere inside the historic building of Paris Observatory, on the banks of River Seine, is stored away, in packing crates, some of the biggest lenses ever manufactured. Two of them measure 49 inches (1.25 meters) in diameter. These lens were once the most critical components of the largest refracting telescope ever attempted.

Construction of the Great Paris Exhibition Telescope began in 1892, within months after the French government announced plans for the 1900 World’s Fair in Paris. The idea was to build a structure as impressive as the Eiffel Tower which was constructed as the entrance to the 1889 World's Fair. These world’s fair, that were being held periodically all over Europe, provided the hosting country, as well as participants, the opportunity to showcase advances they had achieved in manufacturing, science, and technology. Countries would strove for prestige by exhibiting their latest machines and products, their cultural achievements, and imperial possessions.

The Great Telescope, installed, from the ocular lens end.