The middle of the icon looks like an ancient castle with three pillars on top and a passageway underneath. Behind and in front of the central piece are parallel lines that run away and to the castle portion. Behind the central image the lines zig zag whereas the lines in front are smoother and linear.
This is a Great Wall icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,700 icons, all in the same style and quality.