@l i am said:

All your images have a slight, warm, sepia tone. Was that in post processing or acheived some other way?

There is a slider you can adjust on Enscape to add warmth to the image. I also put a warm filter over the hdri in photoshop.

Thank you Liam, sfto1, and CarolineJ!

@mike amos said:

I doubt any of this is new to you seeing as the Romans and Venetians used it. The use of adjustable levels of water could be used instead of soil which may speed up the process but height of tower may be limited. Enlarged concrete foundations with adaptable buoyancy could do the job but it's theoretical. Yours is a fascinating project, thanks for showing it.

Its definitely a unique set of detailing when thinking of all the opportunities and setbacks. Hopefully we don't have to worry about the rise of sea levels in a while.

Brilliant ... where did you get those trees? would you mind sharing them?

Excellent work!