The Arcology radically alters urban architecture by offering near-limitless space - upward. Since <l:6,124>overcrowding<e> is decreased by 8, <l:6,96>happiness<e> ensues. It also greatly increases city's security. Slavers have no chance of penetrating its systems, and any would-be attackers have to deal with megatons of steel, concrete and fuleren to have hope of rooting out the defending forces, which receive a solid Defense bonus of 4.