time capsule

noun2

1. •
   A sealed container, buried at a specific location, that contains records of contemporary life, to be rediscovered in the distant future.
2. •
   (figurative) An object, place, or collection that encapsulates and preserves the characteristics, culture or essence of a particular time period, usually due to isolation or some specific external influence.

   • As we've seen, Belarus is a Soviet time capsule that continues only because Russia is keeping it on life support. — 2011