The Gatchina Palace Egg, made by House of Fabergé, 1901. The egg itself is only 5 inches from top to bottom!
From The Walters Museum description:
When opened, the egg reveals a miniature replica of the Gatchina Palace, the Dowager Empress’s principal residence outside St. Petersburg. So meticulously did Fabergé’s workmaster, Mikhail Perkhin, execute the palace that one can discern such details as cannons, a flag, a statue of Paul I (1754-1801), and elements of the landscape, including parterres and trees. Continuing a practice initiated by his father, Alexander III, Tsar Nicholas II presented this egg to his mother, the dowager empress Marie Fedorovna, on Easter 1901.
I can never get enough of Fabergé eggs.
Reproduced from the Walters Art Museum collection under a Creative commons license.