Ice Castle?

As the canal freezes, many patterns are displayed. Because the canal is a relatively calm body. ice forms without much of an influence from  waves or ripples. This is an area of about 6 square feet of canal surface, looking down from the path. 

Here, my imagination sees birds flying over a cathedral like structure.

Here's a link (click) to a large website displaying and commenting on Snowflakes (ice crystals).