For a long time the walls of Constantinople have stood firm against a wide variety of invaders. It's walls have been widely appreciated for their advanced design and successfulness of course this is not to say that they are the only factor that made Constantinople hard to besiege.
But what I'm curious for is if any European powers made efforts to emulate these walls. After all, according to some, Charlemagne tried to emulate Constantinople by the building of his coty Aachen. With the rise of the cities and the subsequent taking of Constantinople in 1204 it wouldn't be surprising if anyone took some inspiration from their walls.
Well, a great many Medieval cities were walled. Many of those walls, (or sections of them) still survive.
The walls that were perhaps the most conscious emulation of the walls of Constantinople were those of Caernarfon Castle, in Wales, built starting in 1283, by King Edward I.
The bands of colored stone in the walls, and the use of polygonal (rather than round) towers were thought by historian Arnold Taylor to be a conscious use of the imagery of Constantinople, and to also have referenced the legendary dream of Roman Emperor Magnus Maximus, wherein he saw "the fairest fort that man ever saw", within a city, at the mouth of a river, opposite an island, with mountains in the background.
This interpretation is not accepted by all historians.