Formal:
* Mansion: A large, imposing house, often with many rooms and luxurious furnishings.
* Château: A large stately house or castle, especially in France.
* Villa: A large country house, especially in Italy or on the Mediterranean coast.
* Residence: A formal term for a place where someone lives, especially a grand or official one.
* Royal residence: A formal term for a house or building where royalty lives.
* Seat of power: Refers to the location where someone holds power, which could be a palace, but also a government building or other location.
Informal:
* Castle: A large fortified building, often with towers and walls.
* Fortress: A strong building designed for defense.
* Hacienda: A large estate, typically in Latin America.
* Manor: A large country house, especially in the UK.
* Grand house: A general term for a large and impressive house.
* Home: Could be used in a figurative sense, referring to a place of great power and influence.
Literary:
* Abode: A poetic or formal term for a dwelling place.
* Domicile: A more formal term for a place of residence.
* Hall: Can be used to refer to a grand building, especially in a historical or literary context.
The best alternative will depend on the specific context and the desired tone.