Ig-Alima: Green Field Cutting Through the Thousand Mountains (千山斬り拓く翠の地平, Senzangiri Hiraku Midori no Chihei?), the Mountain Felling Sword (斬山剣, Zanzan-ken?), is a gigantic sword classified as a Divine Construct. Like Sul-sagana, it is named after a deity in Sumerian Mythology.
When launched from the Gate of Babylon, it can be used as a large, crushing projectile, and it can be dropped from above an opponent horizontally to crush them with its massive size. It can be laid against a structure to utilize it as a rampart, and multiple people can engage in battle upon its width without difficulty. While normally unable to be wielded, Gilgamesh's gigantic corrupted form is able to wield it along with the Shield of the Gods, allowing it to easily chop through a forest with a single swing until being partially cleaved by Illya's Zwei form.
It still proves to be a potent weapon even afterward, and it remains damaged even after returning to the Class Card's treasury when it was being utilized by Angelica. Shirou Emiya reproduces it with Projection, noted to be a praiseworthy feat by Gilgamesh due to it being a Divine Construct, being called Ig-Alima: Green Field Cutting Through the Thousand Mountains - Fake (虚・千山斬り拓く翠の地平, Nise - Senzangiri Hiraku Midori no Chihei?). However, Shirou's projection of the sword was hollow, thus it wasn't a complete copy of the the Ig-Alima. This might be due to the fact it is a Divine Construct if it is the core of the blade that is made of divine components (which makes sense when you include the fact that the square-cube law says the blade should break under its own weight).