Daurell Caverns is another optional dungeon that you can access in south Duscae, and comes with plenty of tough enemies, including a climatic fight against an Iron Giant.
When you're done, be sure to check out other Final Fantasy 15 dungeons and tombs for more places to explore.
Recommended level: 28 (Note: The recommended level is appropriate for the final boss in this dungeon, but a number of enemies you'll encounter along the way are substantially tougher - it's possible to run past some of them, but you may want to wait until you're well past level 40 before attempting to clear it.)
Head for the winding road on the south edge of the Causcherry Plains in south Duscae, park up on the road directly south of the H in "Causcherry" (or north of the G in "Heights") and follow the path south. When you reach the fishing stand head south east and you'll spot the entrance at the end of the path.
Head inside, and prepare for your first encounter with Necromancers. These guys can outright kill you from full HP, eliminating your "Danger" safety buffer - even with Noctis at level 47 we were one-shotted more than once by these guys. You must block their attacks, and if they grab you then hammer Circle/B for all you're worth as failing to escape from their grip is game over. They're weak to Broadswords, Shields, and Frost, and resistant to Lightning, and they can cause Confusion with clouds of smoke or Petrification with their wide-beam ranged attack, so keep an eye on your party's status effects.
After the fight is over take the left (south west) fork and follow the path round, and climb down at the end to reach the lower level. You'll run into a Ronin and a few Hecteyes (vulnerable to Javelins and Shields, no resistances) along the way, and as you pass down the narrow passageway you'll encounter some green water - it starts cropping up a lot from now on, and it's mildly poisonous so don't step in it if you can avoid it.
When you reach the junction there's a fishing spot straight ahead, and the main path continues to the left. Another Necromancer ambush awaits you just past the junction, and as the corridor widens further down the passageway more Nercomancers, a couple of Ronins, and some Skeletons (weak to Broadswords, Mechanisms, and Frost, resistant to Lightning) will attack.
At the next fork the turning on the right is a dead end and a couple of Ronin will spawn if you explore it, so keep going straight. When you reach the end more Necromancers, Hecteyes, and Ronins will pile in, and the fight is further complicated by mostly taking place in a poisoned puddle, so you may prefer just to hot-foot it into the next area.
Need more help? Our Final Fantasy 15 guide and walkthrough can provide tips on main story, as well as the open-world's many quests and activities. Learning how to get AP fast, EXP fast and money or Gil fast will aid you in many optional dungeons and tombs - including how to open and explore their locked doors. There's also plenty of interesting side-quests, too, such as the Scraps of Mystery and Professors Protege frog locations. And if you want to get around easier, you can rent a Chocobo, learn the infinite sprint trick and later in the game, get the flying car Regalia Type F. There's also more to see and do with DLC, such as Episode Gladiolus and Episode Prompto.
Edge your way around the scaffolding until you find a ladder. Climb down and straight back up again, then continue to follow the scaffolding. Squeeze along the narrow ledge, head up the slope, and confront the Iron Giant.
Iron Giant battle
He's weak to Broadswords and Shields, and resistant to Fire, and he'll be accompanied by a selection of Ronins, Hecteyes, and Necromancers, so the boss is really the least of your worries and you should focus most of your attention on the Necromancers.
Once everyone's dead return to the exit.