Minas Tirith is likely one of best defended fantasy cities. Its defences consist of seven semi-circular walls. These walls, thanks to city being built on a hill, rise above each other, allowing defenders on the inner wall to shoot over the outer wall – and so on for seven levels. Further, a stone outcropping separates all levels of the city except the first and the citadel into half; as a result, Minas Tirith has twelve sectors of defence, which have to be taken in succession for the city to fall. Outer area of the city is protected by the long wall of Rammas Echor, which stretches for miles around the city; but the first and perhaps most important obstacle in reaching the city itself is the great river of Anduin. Its breadth and strong currents prevent it from being crossed anywhere except Cair Andros and Osgilliath, thus funneling enemy forces.
Constantinople is similar to Minas Tirith, but with some advantages and disadvantages. In both cases, starving out the city requires the control of its hinterland – Pelennor and Thrace, respectively – which requires negotiating the outer walls (Rammas Echor / Anastasian Wall). With regards to defences, Constantinople is defended by 45-kilometers-long Anastasian Wall, which is similar in nature and purpose to – and may have inspired – Rammas Echor. Too long to defend properly, it most likely served as a customs border and early warning system. But while Minas Tirith can be completely cut off by land – being miles inland – Constantinople could always be resupplied by sea. Yet its waters were themselves major obstacles due to strong and hard to predict currents, which required experienced sailors to navigate. Both cities also have layered defences, with outermost wall of Constantinople consisting of a total of three walls: the moat wall, the outer wall and the main wall. If Wall of Constantine and Wall of Septimius Severus still existed – which they likely did not by 10th century at latest – this would have meant five layers of defences. City itself however was built upon seven hills, much like Rome.
While depth and extent of defences is similar between Constantinople and Minas Tirith – although with former being much larger, while latter has advantage of an, essentially, magical wall – strategically, Constantinople is much more similar to Osgilliath. Both cities sit on major waterways, which prevent the enemy from fully encircing them unless the enemy in question has a navy. Minas Tirith – nor Minas Ithil, which is likely an actual Constantinople counterpart – has no direct access to any waterways, being miles from Anduin and even further away from the sea. However, fact that Osgilliath sits on Anduin means that it has permanent access to fresh water, while Constantinople depended on aquaeducts. On the other hand, while only one side of each half of Osgilliath is protected by the river, three sides of Constantinople are protected by the sea.
When siege of Constantinople was anticipated in 717., large portion of population was evacuated – something Denethor also does, although the same was also done before the siege of Vienna in 1683.