Cadmus Island was a prison developed by Cadmus Laboratories to contain the prisoners of war of the Earth 2 War. It was a highly secure area, guarded by the OMAC Security System, Deathstroke the Terminator, Grifter and Fifty Sue. FBI agent King Faraday was known to have connections to the leaders of the island. Aside from the OMACs, the Earth 2 prisoners were guarded by pressure sensitive plating which was keyed to motion detection systems which were keyed to sound detection systems. The subbasement of Cadmus Island was designed to be a holding cell for normal people from Earth 2 and have them upgrade the OMACs.
When Futures End occured, the Eye Future and the End Future were both averted. As a result, the Earth 2 War never happened and Cadmus never constructed their island.