Nothing like the hexagon has ever been seen on any other world.

The structure, which contains a churning storm at its center, is about 20,000 miles wide and reaches roughly 60 miles down into Saturn’s atmosphere.

The bizarre hexagonal cloud pattern was first discovered in 1988 by scientists reviewing data from NASA’s Voyager flybys of Saturn in 1980 and 1981, but its existence was not confirmed until NASA’s Cassini spacecraft observed the ringed planet up-close years later. The entire structure is large enough for four Earths to fit inside. 

• The magnetic field of Saturn is nearly 578 times more powerful than Earths
• Saturn is the least dense planet in our Solar System
• Saturn has 53 named moons
• Saturn gives off more than twice the energy it receives from the Sun

An update, as of 2018:

A new high-altitude vortex with a hexagonal shape has appeared akin to the famous hexagon seen deeper down in Saturn’s clouds. This suggests that the lower-altitude hexagon may influence what happens up above and that it could be a towering structure spanning hundreds of kilometres in height.

Its properties were revealed in detail by Cassini, which observed it in multiple wavelengths — from the ultraviolet to the infrared — using instruments including its Composite Infrared Spectrometer (CIRS).