Helsinki-Tallinn railway tunnel
 

I have read on the internet about this prosject.
So what do we think about this?

It's seems like it will be build with track guage 1435 milimetre

This will be a further expension of Rail Baltica (http://www.railbaltica.org/) which is a planned railway route from Warsaw to Tallinn.

https://www.railway-technology.com/projects/helsinki-tallinn-railway-tunnel-gulf-of-finland/

https://emerging-europe.com/intelligence/tunnel-vision/