The Ho Phra Nak (หอพระนาก) is a royal mausoleum on the northwestern side of the temple. It was previously a Buddha image hall and was built by Rama I to house the sacred Phra Nak Buddha image from Ayutthaya, which was made of gold and copper. Even though the image was eventually moved to the Wihan Yot, the name remained. The hall is rectangular, with an entrance hall on the east side. The roof is covered in green and orange tiles. Inside, the hall is divided into seven rooms. Ashes and remains of members of the royal family are kept here. Formerly, only the ashes of female royalty was kept here, as was the tradition at Ayutthaya. Later, however, the ashes of many senior male members were also kept here as well. Notably, it contains the ashes of all the viceroys of the Chakri dynasty and their princely descendants. These ashes are kept in hundreds of individual gold urns.