While landmines are technically "banned" weapons, there are still plenty in use, and one of the most mined areas is Korea. The Mine Ban Treaty came into force in 1999, but 42 countries did not agree to the ban on the production, stockpiling, and use of antipersonnel mines. Countries who opted out include China, India, Pakistan, Russia, South Korea and the United States. This includes the major producers of landmines, as well as many of those still using landmines.
South Korea has about a million landmines emplaced along the DMZ (DeMilitarized Zone) between north and south Korea. The U.S. and South Korea have another two million or so mines in storage, in case North Korea tries to invade again (as it last did in 1950.) North Korea won't say how many mines it has planted, but it's probably at least several hundred thousand.
South Korea has to replace mines as they get too old to still work, and they are starting to do this with a new generation of command (by wire or wireless) detonated mines. Many of the more recent mines South Korea has stockpiled are of the self-destruct (a certain amount of time after planted) variety. South Korea has been making plans for clearing all the mines it has planted over the years, largely because it appears that the communist government of North Korea will collapse soon, eliminating the need for the DMZ, and all those mines.