Route 1

Running alongside the Carinos River, Route 1 rises and falls with the gentle rolling hills of the Athaliá plains. Generally calm and warm, the path is flocked with groves of wild Violé berry trees and the occasional villa with cypress trees.

Walking Path

Sticking to the cleared path is the best chance to run into fellow travelers and residents for conversation or battle. A few flocks of wild Starly roost in the olive branches and the occasional Rattatta scampers over the trail from grass to grass. At night, a rare Hoot-Hoot or Noctowl will pass overhead the closer you are to Athaliá.
Using this path it is about a 2 day hike to the Celesta Ruins.
Pokémon Found here

Pokémon	Time of Day	Rarity
Hoot-Hoot	Night	Rare
Nidoran	Day	Very Rare
Noctowl	Night	Very Rare
Rattatta (Alolan)	Any	Common
Starly	Day, Evening	Rare

The Ancient Path

For the more adventurous, close to Athaliá there is a stone marker that begins an ancient and somewhat overgrown cobblestone path. With tall grass on either side, this path is less traveled and wild Pokémon scamper back and forth. Periodically, you might stumble upon a scraggly oran berry tree and grepa berry vine.
Nidoran often make their home in the grasslands munching on berries. In the rare Thunderstorm for the area, Shinx have been known to make an appearance. In very rare cases, a lone Riolu may venture out to train alone.
Using this path it is about a 3 day hike to the Celesta Ruins. About 4 hours down the path from Athalia is an ancient stone mosaic overlooking a small salt water spring. Long ago this site was considered to be the icon of Athalia though the ancient olive tree was eventually chosen instead.
Pokémon Found here

Pokémon	Time of Day	Rarity
Hoot-Hoot	Night	Rare
Nidoran	Day	Common
Noctowl	Night	Very Rare
Rattatta (Alolan)	Any	Very Common
Riolu	Any	Very Very Rare
Shinx	Morning, Day, Evening	Very Rare (Thunderstorm only)
Starly	Day, Evening	Very Rare

Riverside

No designated path exists along the river, though a few well known fishing spots do exist. Wild Azuril and Marill often can be seen playing in the water though are often shy and will hide as people approach. The river is home to Magikarp and the occasional Corphish.
Should you attempt to walk along the river the whole way, it is about a 4 day hike to the Celesta Ruins.
Pokémon Found here

Pokémon	Time of Day	Rarity
Magikarp	Any (Fishing)	Very Common
Corphish	Morning, Evening, Night (Walkling, Fishing)	Uncommon
Azuril	Morning, Day	Very Rare
Marill	Morning, Day	Uncommon
Starly	Day, Evening	Very Rare

Trainers and NPCs

South Exit: Athalia City
North Exit: Ruins of Celesta