Because furfoot didn't give complete info on the good maps, I thought I would. The following info is based off of the save located here: (http://dq9.ffsky.cn/etc/dq9famousmapssav.zip) that is mentioned in this
Gamefaq thread. It is a Japanese save with all the famous Japanese maps.
Here is a list of all the best maps in the game: (location, map number 1, map number 2)
115, 134, 30804 (Floor 11 is full of Metal King Slimes, Boss = Lucid) Silver Marsh of Bane Level 58
6, 175, 2720 (Floor 7 is full of Metal Slimes, Boss = Fowleye) Steel Path of Bane Level 69
2, 248, 4929 (Lots of A/S Chests, Boss = Trauminator) Sapphire Maze of Doubt Level 75
7, 189, 200 Bronze Crypt of Hurt Level 77
105, 184, 9638 (Good chest map for crafting, Floor 9 is Metal King Slimes, Boss = Hammibal) Silver World of Dread Level 79
47, 198, 25615 Emerald Snowhall of Hurt Level 81
12, 217, 26468 (Great money farming map gem slimes for 10k per kill, Boss = Greygnarl) Sapphire Glacier of Bane Level 81
87, 187, 9788 Emerald Dungeon of Fear Level 85
90, 183, 15522 (Kawasaki loot map, Boss = Fowleye) Emerald World of Gloom Level 86
84, 187, 3676 (Masayuki map, Floor 15 has Metal King Slimes, Boss = Tyrannosaurus Wrecks) Ruby Path of Doom Level 87
34, 184, 18322 (Good chest map) Ruby World of Dread Level 89
120, 183, 6129 (Super hard trash mobs and highest level dungeon) Emerald Waterway of Hurt Level 99
There are other maps listed in the save (legacy bosses I think), but they are not listed here.