In the construction of the new royal palace, Arthur had considered building an underground air-raid shelter, or more precisely, an underground safety base, but it seemed unnecessary at the moment.
Firstly, the island chains surrounding Australasia had already determined that foreign aircraft were basically unable to enter the mainland of Australasia.
If the native land of Australasia was truly threatened, it would be facing a world-wide war, or even a full-scale nuclear war.
Not to mention how far away that time might be from now, even if a supposedly safe underground air-raid base was built now, it might not necessarily withstand the attacks of the weapons at that time.
Especially in the case of air-raid shelters specifically designed to protect against nuclear weapons, as technology advances, various radiation-proof materials will also be gradually invented.