2,300 rooms total

Photo from Wikimedia Commons
Palace of Versailles
The extravagant seat of French monarchy outside Paris/World Landmarks
The Palace of Versailles, built and expanded from 1661 under Louis XIV, is one of the most opulent royal residences ever constructed. The palace has 2,300 rooms spread across 63,154 square meters of floor space. The famous Hall of Mirrors is 73 m long and contains 357 mirrors. The gardens, designed by Andre Le Notre, cover 800 hectares and include 1,400 fountains. Versailles served as the seat of French government from 1682 until the French Revolution in 1789 and was where the Treaty of Versailles was signed in 1919.
Measurements
800 hectares of formal gardens
Garden-facing facade
357 mirrors reflecting 357 windows
Cruciform water feature
Including all grounds and parkland