Step 1: Understanding the Concept:
The question seeks to identify the specific period in Mughal history when architectural splendor was at its peak, particularly with the use of white marble.
Step 2: Detailed Explanation:
The reign of Shah Jahan (1628–1658) is known as the Golden Age of Mughal Architecture.
He moved away from the red sandstone used by his grandfather Akbar to white marble decorated with Pietra Dura (inlay of semi-precious stones).
His most famous masterpiece is the Taj Mahal in Agra, but he also built the Red Fort (Delhi), the Jama Masjid (Delhi), and the city of Shahjahanabad.
Step 3: Final Answer:
Shah Jahan is the emperor whose reign is the golden age of Mughal architecture.