The area in which the Royal Mausoleum is located is known as Mauna 'Ala.
This is where Kamehameha I defeated the armies of King Kalanikupule for control of the Hawaiian kingdom in 1795.

The original Mausoleum was located on the grounds of Iolani Palace.
Kamehameha IV ordered a larger one built in the current location because the Iolani Palace Mausoleum was getting overcrowded.
With the exception of Kamehameha the Great amd Lunalilo, all of Hawaii's royalty are entombed in Nuuanu.
This Mausoleum building was converted to a chapel in 1922.