What is the word for a magnificent history?

Solution 1:

Golden age

noun

1) the most flourishing period in the history of a nation, literature, etc.

Source: Dictionary.com

Solution 2:

Epoch may be the word you are looking for.

Epoch means: A long period in which new and great developments take place.

For example we say:

The development of steam engine marked an epoch in the history of Industry.

The rule of the Gupta Dynasty is considered an epoch in Indian History.

In view of the above examples I think epoch is the suitable word in the context.

Here is the link.

. https://dictionary.cambridge.org/dictionary/english/epoch