These places are called Hidden Hollows. These are places where you can get DW ability Pokemon ingame. Meaning that Miccino you fainted has Skill Link. There are many places like these.
Look here under Hidden Hollows to see the areas and Pokemon inside them.
Oh yeah, sometimes there can be items instead of Pokemon. You may need the Dowsing Machine.
I'll put the list here for reference.
- Nidoran M/F (Hustle), Granbull (Rattled), Watchog (Analytic)
- Lombre (Own Tempo), Manectric (Minus), Bibarel (Moody), Pachirisu (Volt Absorb), Zebstrika (Sap Sipper)
- Liepard (Prankster), Mincinno (Skill Link), Foongus (Regenerator)
- Woobat (Simple), Foongus (Regenerator)
- Watchog (Analytic), Cubchoo (Rattled), Zangoose (Toxic Boost), Seviper (Infiltrator)
- Muk (Poison Touch), Liepard (Prankster), Garbodor (Aftermath), Bouffalant (Soundproof)
- Tangela (Regenerator), Spheal (Oblivious), Drifloon (Flare Boost), Skorupi (Keen Eye), Foongus (Regenerator)
- Fearow (Sniper), Kingler (Sheer Force), Dragonite (Multiscale), Chatot (Big Pecks)
- Pelliper (Rain Dish), Amoonguss (Regenerator), Mienfoo (Reckless)
- Golduck (Swift Swim), Gligar (Immunity), Zangoose (Toxic Boost), Seviper (Infiltrator), Absol (Justified)
- Marill (Sap Sipper), Dunsparce (Rattled), Herdier (Scrappy)
- Butterfree (Tinted Lens, White 2), Beedrill (Sniper, Black 2), Poliwhirl (Swift Swim), Murkrow (Prankster), Breloom (Technician), Hariyama (Sheer Force), Medicham (Telepathy), Bagon (Sheer Force), Amoonguss (Regenerator)
- Pinsir (Moxie), Heracross (Moxie), Combee (Hustle), Leavanny (Overcoat)
- Clefairy (Friend Guard), Ditto (Imposter), Sneasel (Pickpocket), Metang (Light Metal)
- Vulpix (Drought), Golduck (Swift Swim), Swablu (Cloud Nine), Bronzor (Heavy Metal), Amoonguss (Regenerator)