Also known as the Fifth Dimension, the Space-Time Vortex is the foundation upon which the first four dimensions are built. It is this fact which enables Time Travel Capsules to move from Minkowski Space and integrate into the Fifth Dimension. Unlike the first four dimensions the fifth (and sixth-eleventh) dimension is collapsed and folded into a space the size of an atom. Time is made up of individual particles called Chronons. It is possible to transmat objects through space by breaking the object down into light-waves and pushing them through the space between the time particles. When plotted out in three dimensions the Vortex appears to be a glittering blue void with gold highlights. There is no air pressure within the Vortex and the time winds are such that they would destroy any normal matter by aging it until complete structural breakdown occurred. Block-Transfer objects are immune to the normal Vortex energies. While most humanoids would die in seconds if immersed in the Vortex some Time Lords can survive in the Vortex by using a technique called Vortex-Walking. Artron Energy can exist in the Vortex, and indeed it is the Artron Energy of every sentient in the Universe that makes up the Web of Time.

Even for TARDISes vortex travel isn't entirely safe. They are subject to surges in the Vortex called Time Spillage. These discharges of energy in the Vortex come from and go to nowhere. A TARDIS uses Vortex Shields to protect itself and uses Muon based counter-magnetization to navigate this and other turbulence. Most TARDISes can handle Time Spillage with a rating of 7 on the Bocca Scale, but if overloaded a TARDIS will attempt an Automatic Emergency Landing. A TARDIS that is trapped by a Spiral Nebula's gravity field will need carefully plotted escape coordinates to break free. Other dangers include massive black holes in the Multiverse (which cause random gravity lenses), monopole turbulence (often created by starship plasma drives), Tuckson-Jacker force fields (often used in weather control systems), quantum mirages, substrate diversions in the Vortex, and crossing the Time Spiral boundary. If a TARDIS was to be trapped between a Vortex Rupture and a Subspace Infarction it would break up. There are also uncharted areas of the Space/Time Vortex. The Mandragora Helix inhabits one such area. The Mandragora Helix is a spiral of pure energy radiating outwards in ways the Time Lords don't fully understand. This energy is sentient and has a relationship to the position of the stars. It is also possible (but very rare) for a TARDIS to become trapped in a fractional dimension between the Vortex and N-Space. But the Vortex is not just a danger to a TARDIS. A TARDIS is also a danger to the Vortex. A mortally wounded TARDIS could rip a hole in the vortex as it traveled.