The Argolis Array was a large Dominion sensor array located in the Argolis Cluster. The array was extremely powerful, able to monitor movements across five sectors and detect cloaked ships within two light years.
Three months in the Dominion War the Federation became aware of the array's existence and sent the USS Defiant to destroy the array. The Defiant was able to sneak up to the array by traveling through the hazardous Argolis Cluster instead of around it, though the gravitational eddies damaged the ship's warp drive. The crew then created a false reading that showed over a dozen Starfleet cruisers approaching to draw the defenders out of position. The Defiant was then able to get close to the array and destroy it with a salvo of quantum torpedoes. The resulting explosion crippled or destroyed the defending ships allowing the Defiant to escape at impulse. (DS9: "Behind the Lines"; The Dominion War Sourcebook: The Fires of Armageddon)