The Mercantile Library of Cincinnati has a 10,000-year lease. When Cincinnati College burned in 1845, the young men of the city’s Mercantile Library Association helped to rebuild it. As a reward, the library was given a lease of ten millennia on the 11th and 12th floors of the Mercantile Library Building in downtown Cincinnati.

The current lease will expire in the year 11845 — but it’s renewable.