Why were only 13 emperors buried here?

More than 100 years after Emperor Zhu Di decided to start construction of the Ming Tombs, 13 out of the 16 emperors of the Ming Dynasty were successively buried in this basin which was later called "13 mausoleams of the Ming Dynasty". But, Why only 13, not 16 emperors were buried here? Where were the other 3 emperors?

The first emperor Zhu Yuanzhang, who. founded the Ming Dynasty, made Nanjing the capital andN as a result, he was buried in anjing after he died. The mausoleum of the first Ming Emperor and his empress is not as impressive as the ones we are going to see today, but when you are in Nanjing, you can still go there. It is worth a visit.

The second emperor, Zhu Yuanzhang's grandson, had no known mausoleum, he tried to weaken the forces of his uncle, the Prince of Yan ( the fourth son of the first emperor) but was met with strong counter-attacks three years later, he was ousted and no one knew his whereabouts. His uncle became the third emperor of the Ming Dynasty and moved the capital to Beijing.

The seventh emperor Jingtai was buried in the Hill of Gold, the west suburb of Beijing. Why was his mausoleum built in the Hill of Gold? There s a story about it.

When the Sixth Emperor, Yingzong, was in his 14th year of reign, Mongols from the north invaded the country. Yingzong led personally the expedition to conquer the Mongols, largely due to the persuasion of those eunuchs. Unfortunately, he was captured by those mongols in 1450, and his brother took over the throne.

Several years later, Yingzong was set free by the Mongols and managed somehow to return to Beijing in 1457. When he returned, he found his throne was seized by his brother. Coincidently, his brother soon became very sick. Yingzong took advantage of his sickness and overthrew him and reproclaimed himself as the emperor. After his brother Emperor Jingtai died, Yingzong refused to honour him an imperial burial. That is why Emperor Jingtai was only buried as a prince in the Hill of Gold.