Drill Tunnel - Digimon World 1
The Drill Tunnel is often the second or third location players enter, you can find this location in the western part of Native Forest. Before we can recruit any Digimon here we'll need to do a short story segment, I talk about this in my Meramon section below but I will mention it here too.
Initially, you can't explore much in the Drill Tunnel. You will need to battle the Drimogemon in the residential area and then speak with the other Drimogemons who are digging in the area. After doing all of this you'll still need to wait until they clear a tunnel. Once the tunnel is cleared you'll need to use a Champion Digimon to move a boulder, then speak to another Drimogemon and wait a bit longer.
Later in the game you will have your final battle with Ogremon here as well. You'll also find Leomon's Stone tablet here which is required for recruiting him; after obtaining this tablet you will find Nanimon at this location too.
Meramon
Requirement: Defeat Drimogemon in the residential room then speak with the one digging. Also need a Champion Digimon to move a boulder.
To unlock Meramon you will need to speak with the Drimogemon in the western 'residential' room and beat him in a fight. You now have two options, you can wait 5 days or you can assist another Drimogemon with moving dirt out of the tunnel for 500 Bits each. Helping to clear the dirt will earn you some Bits and it will reduce your wait time from 5 days to 1 day instead.
Once all of the dirt has been removed you'll find a big rock here that can only be moved by a Champion Digimon. If your Digimon meets the requirement you'll get a short scene of the rock being moved and you can find Meramon by following the linear path.
If you're struggling with raising a Champion Digimon or better I recommend you check out my How To Raise A Digimon Guide.
Drimogemon
Requirement: Recruit Meramon
After defeating Meramon and having him join your city the lava in his room will cool off and you will be able to explore more. You'll find a Drimogemon to the southwest in this area - there will be tons of items to the north of him hidden through the area. When you speak with him, he'll tell you that he is almost finished - so come back 3 days later and speak with him again.
When you return later and speak with him a second time he will join your city. Drimogemon will create a Treasure Hunt shop in town.
Ogremon (Encounter #4)
Requirement: Defeat Ogremon at each of the three other areas to make him spawn here
Ogremon Locations:
1. Great Canyon, run towards the elevator and he will ambush you
2. Great Canyon, take elevator or ledge down to canyon floor and scare the Agumon you see down here and then follow him inside
3. Freezeland, talk with Whamon to travel to his cave, you'll find Ogremon here
4. Drill Tunnel, Ogremon will take control of the Drill Tunnel. Enter and beat him the final time to make him join you.
Once you have taken out Ogremon at the three other locations he will take control of Drill Tunnel. You'll find him at the four way split near the entrance, he isn't difficult to find and the final fight with him isn't too hard either. Defeat him and his Agumon henchmen and he'll join your city.
Nanimon
Requirement: Obtain Leomon's Tablet and then return to this location
After you've obtained Leomon's Tablet exit the Drill Tunnel completely. The next time you return to Leomon's Ancestor's Cave you'll find Nanimon in the area pictured above. If you'd like to learn more about Nanimon and the locations he is found check out my Nanimon Recruitment Guide for more information.
All Nanimon Locations
1. Ancient Dino Region in the same area as Meteormon.
2. Ogre Fortress, found in the boss room where we battled Ogremon.
3. Leomon's Ancestor's Cave in Drill Tunnel, search the area where you get the tablet.
4. Toy Town, in the boss room.
5. Factorial Town, in the sewers north of where Numemon is found.