Most people have never heard of Mondol Beach. Mong-dol is defined in the Korean dictionary as a round stone that is flawless. Mong-dol beaches are full of such stones, and there are many of them in South Korea, there are two main ones in Jeju. One of them is Aljakji Beach which is the most famous in Jeju.

Aljakji is a combination of the Korean word for round and the Jeju language for stone. The round pebbles were transported and deposited from the valley, and over a long period of time, they were carved by the waves while being transported to Aljakji through Musu Stream and Woldaecheon Stream, giving the pebbles a round shape. Professional photographers are drawn to the exotic landscape of it with its dark, rounded boulders and pebbles, and crashing waves. In recognition of its uniqueness and beauty, it was designated and protected as a Jeju City Cultural Heritage Site in December 2003.

It is located in Naedo-dong, next to the coastal road past Iho-Tewoo Beach. Despite having a lot of people right next to it, it is secluded and quiet and is often visited by Jeju residents who want to take a break from their daily routine. There is a parking lot at the Aljakji breakwater nearby, so it's easy to get there by car. It’s a hidden gem in Jeju.

Another mong-dol beach on Jeju is Mojinee Mong-dol Beach. Located on Hachuja-do, this beach is made up entirely of mong-dol without any sand, so people can enjoy a secluded atmosphere without many people.

However, it is important to note that it is forbidden to take away any mong-dol when visiting these two sites. In addition there’s a fine for stealing mong-dols. So visitors need to be careful when visiting these two places.