Some have said visiting one tomb is enough as they are all similar. Yes and no, each tomb follows a general pattern, yet most of the tombs have subtle variations. More importantly its hard to get the scope of the Royal Joseon Tombs with one tomb visit, because part of the wonder of these tombs is the sheer number of them and their care in location and artistry.
Each tomb also tells a story, Prince Sado in particular, tragic and disturbing, but honored by his son. King (Emperor) Gojong's Tomb, as the Joseon Dynasty faded, his tomb is a visage of grandeur. King Danjong's tomb in Gangwon-do is the most unconventional location and layout, this is because he was removed from power and exiled.
13/18 Tomb Clusters
*Donggureung Cluster (Visited 2008)
*Gwangneung Cluster (Visited 2008)
*Yeongneung Cluster (Visited 2008)
*Taereung Cluster (Visited 2008)
*Seolleung Cluster (Visited 2008, 2016)
*Heolleung Cluster (Visited 2011)
*Hongyureung Cluster (Visited 2011)
*Sareung Cluster (Visited 2011)
*Seooreung Cluster (Visited 2011)
*Seosamreung (Visited 2011)
*Uireung Cluster (Visited 2016)
*Yungneung Cluster (Visited 2016)
*Jangneung (Gangwon-do) Cluster (Visited 2016)
Having visited about 13 Joseon Dynasty Tomb clusters in 2008, 2011, and 2016. The sites are extremely peaceful. Perhaps, the most impressive is Donggureung which contains 17 tombs and the first King of Joseon, Taejo. Gwangneung and Yungneung are also worthwhile sites to visit because of their exceptionally beautiful setting. In the small city of Yeoju you can visit the tomb of King Sejong, probably the most celebrated Joseon king, who helped develop the Korean Writing system (Hangul). Several tombs have now added small museums, which often show an excellent video explaining how these tombs were constructed.
One great quality of each tomb is their location, which was carefully chosen. Most Joseon tombs are relatively easy trips from Seoul and provide a relaxing atmosphere and time for reflection. I had a great time taking the metro train (or bus) all over Seoul searching out the next tomb, now the tombs are even easier to visit with its WHS inscription. Definitely a world class site amongst the royal tomb properties included on the world heritage list.