That's a merp map which was a sort of roleplaying boardgame that invented a lot of stuff where there were gaps in the lore. If you compare their pelargir map and the notes of tolkien on pelargir looking like venice, you will see that thy look quite different.
While merp is a nice input and source for stuff, it's not always lore accurate.
Just so you know. Nice to see the map though, didn't know they had a linhir detail map.
In this case there isn't any lore on the aesthetics of linhir so we can do what we like.