Question: This is all horribly nebulous, and I understand it.

But are there any examples in history, when any existing empire had dissolved and was afterwards recreated to more or less the same territory it occupied during its peak for any meaningful period of time (let's say 50+ years)?

I welcome suggestions about how to make this question more precise, but obviously I am looking into current aspirations of some people in Russia, who speak of "uniting Russia" to its historical 17th century borders.

Answer: 
The Eastern Han dynasty was an empire that was founded in 25 A.D. and can be considered as a recreation of the Western Han dynasty. The founder of the Eastern Han dynasty: Emperor Guangwu was a descendant of Emperor Jin of the Western Han dynasty. The Western Han dynasty was dissolved by Wang Mang who created the Xin dynasty after deposing the last Western Han Emperor. Emperor Guangwu led an uprising and restored the Han dynasty.

Western Han dynasty map:
[![enter image description here](https://i.stack.imgur.com/XnjUd.png)](https://i.stack.imgur.com/XnjUd.png)

Eastern Han dynasty map:
[![enter image description here](https://i.stack.imgur.com/21ake.png)](https://i.stack.imgur.com/21ake.png)
The [Second Turkic Empire](https://en.m.wikipedia.org/wiki/Second_Turkic_Khaganate) was founded in 682 CE, about 50 years after the end of the [First (Eastern) Turkic Empire](https://en.m.wikipedia.org/wiki/First_Turkic_Khaganate).

The [German Reich](https://en.wikipedia.org/wiki/German_Reich)
was founded in 1871, about 65 years after the end of the [Holy Roman Empire](https://en.m.wikipedia.org/wiki/Holy_Roman_Empire).

Plus there are of lots of current nation states that trace their roots to some previous kingdoms (or similar) and that at some point were incorporated into other states. E.g. Poland, Portugal, Korea, Egypt, Israel etc etc.