What was the reason behind building the Taj Mahal on the banks of the Yamuna River?

The exact rationale for building the Taj Mahal was not for
the river's honor.  It is here where we have to presume that the significance of the
river was understood at the time and then merge it with the building of the monument to
fully grasp how the Yamuna plays a role in the narrative of the Taj Mahal.  The history
of the Yamuna might be indicative of the answer.  The Yamuna is seen as the largest
tributary that feeds into the Ganga.  In this fact, the Yamuna rises above all, similar
to the Taj Mahal and all other monuments in India.  Additionally, the narrative of the
Yamuna is seen as the result of the alliance between Surya, the Sun God, and the sister
of Yama, the God of Death.  In this, one understands how there is a combination of the
radiant force of life and the inescapable presence of death.  The Yamuna combines both
of these realities, as does the Taj Mahal.  Built as a monument by Shah Jahan to his
wife who died in childbirth, the monument captures both forces of existence in love and
death.  The radiance of the couple's fourteenth child collided with the death of Mumtaz 
Mahal.  In this convergence of pain and beauty, the Taj Mahal and the Yamuna share
similarities in both representing mortality.