Lisbon, Portugal
11th century
Sintra, Portugal
8th century
Braga, Portugal
11th century
Guimarães, Portugal
10th century AD
Idanha-a-Nova, Portugal
1171
Vila Nova de Cerveira, Portugal
13th century
Caminha, Portugal
13th century
Ponte da Barca, Portugal
13th century
Melgaço, Portugal
1170
Melgaço, Portugal
9th century AD
Póvoa de Lanhoso, Portugal
11th century
Monção, Portugal
1306
Monção, Portugal
14th century
Celorico de Basto, Portugal
11th century
Barcelos, Portugal
10th century AD
The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.