Who was Wu Zetian buried with?

Wu Zetian was buried together with Tang Gaozong Li Zhi.

On November 26, the first year of Shenlong (December 16, 705), Wu Zetian died of illness in the Xianju Hall of Shangyang Palace at the age of eighty-two. The imperial edict omitted the imperial title and called it "Queen of the Great Sage of Zetian", and pardoned the relatives of Queen Wang, Xiao Shufei and Chu Suiliang, Han Yuan and Liu Shi. In May of the second year of Shenlong (706), he and Gaozong were buried in the Qianling Mausoleum.

The wordless monument is located in the Qianling Mausoleum (today's Qianxian County, Shaanxi Province) where Wu Zetian and Emperor Gaozong of the Tang Dynasty were buried together. The entire cemetery is modeled after Chang'an City in the Tang Dynasty. There are two tablets in front of the tomb, one is Gaozong's tombstone with Wu Zetian's inscription on it; the other is Wu Zetian's wordless tombstone.

Extended information:

Qianling Mausoleum is a unique mausoleum in China and even the world where emperors from two dynasties and a couple of emperors are buried together. Buried inside are Gaozong Li Zhi, the third emperor of the Tang Dynasty, and Wu Zetian, the only female emperor in Chinese history. It is a key cultural relic protection unit in the country. It was built in AD 684 and took 23 years to complete. Qianling Mausoleum was originally the mausoleum of Li Zhi, Emperor Gaozong of the Tang Dynasty, and was named Qianling Mausoleum. In fact, it is the joint burial tomb of one emperor and one empress.

Since Guo Moruo, modern people believe that this is the tomb of two emperors buried together, but this is not in line with the ancient views (including those of the Tang Dynasty). Because after the Shenlong Coup, Wu Zetian was forced to return the country of Tang Dynasty to the Li royal family.

In order to have a place to live after her death, Wu Zetian announced that she would abolish her imperial title and asked her son (Tang Zhongzong Li Xian) to bury her in the Qianling Mausoleum of Tang Gaozong as Empress of Tang Gaozong. Tang Zhongzong agreed to his mother's request. Therefore, in terms of etiquette, the Qianling Mausoleum still belongs to the joint tomb of one emperor and one empress.

Reference: Baidu Encyclopedia-Wu Zetian