#4. It took approximately 22 years and $1 billion
The construction of the Taj Mahal was begun in 1632, a year after the death of Empress Mumtaz. The construction was completed in the year 1653, which means that it took approximately 22 years to complete this astounding piece of architecture. At that time, the estimated construction cost was a whopping sum of Rs. 32 million, which, when considered in terms of today’s value of money, would be something way above $1 billion.