The Library was an unreleased building that reduced the cost of all new technology by two stars per friendly adjacent temple. It was unlocked by the Philosophy technology, cost five stars, and could only be built on field tiles.
The Library was only present in certain beta builds for version 1.7 "Power", and was never released to a public build. It was effectively replaced with the Literacy bonus, which reduced research costs by a flat 25% (final cost rounded up). This discount is now 33%.
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A level 1 Library
A level 2 Library
A level 3 Library
A level 4 Library
A level 5 Library
A level 6 Library