The structure and the period which the embankment was built were discovered. 和 The structure of the embankment and the period in which the embankment was built were discovered 的差別在哪裡？如果不好說明，請提供一些例句。

The structure of the embankment and the period in which the embankment was built were discovered.

This is a more complete sentence, it is clear and easy to understand. The first sentence is the shorter form:

The structure and the period which the embankment was built were discovered.

But it has some issues with grammar and phrasing, which makes it sounds awkward/unnatural to me. I would phrase it as:

Both the structure itself and the period in which the embankment was built were discovered.