A Suliban helix was a massive spiral-shaped space station used by the Suliban Cabal. Helices were formed by combining of hundreds of cell ships, as well as other cell ship like components, around a central core, and was capable of housing at least 3,000 personnel.
Enterprise discovered one located in a class seven gas giant while searching for the Klingon Klaang. Located aboard the helix was a chamber used by Silik for communicating with his master from the future. The helix's cell ships were separated once the polarity of the maglocks was reversed by Captain Jonathan Archer. (ENT: "Broken Bow")
After Archer and Travis Mayweather had been exploring some strange energy readings near a Tandaran moon, they were captured by the Tandarans. When they saw the Suliban who were detained with them at Detention Complex 26, Archer thought that the energy readings might have come from a helix. (ENT: "Detained")
Another helix was later found in a deep red nebula near Paraagan II. It was from here that the Cabal's mission to destroy the Paraagan mining colony was planned. After being captured by the Cabal in March of 2152, Enterprise was taken to this helix, though it later escaped. (ENT: "Shockwave, Part II")
The original helix in "Broken Bow" had a unique cell component not seen in the other helix in "Shockwave, Part II". This cell was similar to the spherical cell ships, but had an elongated central section. If this was a ship like the others, it would be a step between the spherical and cylindrical cell ships.