What does this poem mean?

"Willow Branches" by Han Cong of the Tang Dynasty:

The Dongyuan built by King Liang Xiao of the Han Dynasty and the embankment built by Emperor Yang of the Sui Dynasty to open the canal have become smoke in the past, but there are many flowers in the garden. Thousands of willow branches on the embankment are still dancing in the spring breeze. Why bother thinking about the past and future events that took place thousands of years ago? Who would have thought that Yang Hua would fly into the Han Palace a thousand years later?

"Liangyuan Sui Embankment" is a classic of chanting historical sites.

Yanghua refers to catkins and spring scenery. The meaning of the whole poem is, will there still be such spring scenery in the Han Palace in a few years?