The Middle Ages defence wall of Torun long for about 4 kilometers was on average 1,2 metre thick and 6 metres high. Each of the organism of eternal Torun had its defence wall system together with the gates and the towers: Old Town, New Town and Teutonic Knights' Castle . One of the hypothesis tells that the Old Town was surrounded by a double wall: high wall and low wall with a moat before. The land built between the walls was called among-wall. On the high wall city side there was a guard's porch . The building of the wall was very characteristic: a brick face and the interior filled in with fieldstones joined by a calcium mortar. During many centuries the wall system kept his role but only the artillery development reduced its military function.