After you defeat Commander Jupiter in the Team Galactic Eterna Building, you can get a bike and ride south on Route 206, also known as Cycling Road.
Trainer Battles
As you go south, you may encounter trainers. The first trainer is Cyclist Axel, who is facing the right side of the bridge, and has a level 17 Staravia. You get 816 Pokédollars for winning.
The second trainer is Cyclist Megan, who is on the left side, and has a level 17 Shinx. You get 816 Pokédollars for winning.
Next is Cyclist James, who is facing the left side of the bridge and has a level 17 Ponyta. You get 816 Pokédollars for winning.
Next is Cyclist Nicole, who is riding left and right, and has a level 15 Starly and a level 15 Ponyta. You get 780 Pokédollars for winning.
Next is Cyclist John, who is facing the right side of the bridge, and has a level 15 Starly and a level 15 Staravia. You get 780 Pokédollars for winning.
Next is Cyclist Ryan, who is on the left side of the split, and has a level 17 Zubat. You get 816 Pokédollars for winning.
Next is Cyclist Rachel, who is facing the right side of the bridge, and has two level 15 Shinx. You get 780 Pokédollars for winning.
Next is Cyclist Kayla, who has a level 17 Pikachu. You get 816 Pokédollars for winning.
Free Stickers
Go south from there and enter the building. Talk to the person in the middle to get 3 Sky Stickers B. Then go south to reach the lower part of Route 206.
Route 206 Part 2
From here, there are two berry trees to the left, and you can use Cut on the trees on the right to access the area of Route 206 that goes beneath the cycling road.
In this area, you can catch Bronzor, Geodude, Kricketot (only in the morning), Kricketune, Ponyta, Stunky (Brilliant Diamond only), and (only at night) Zubat.
As you go north, cut down the tree on the right and check the ground past where it was, and you will find a Full Heal.
There is a hidden Elixir to the right of a Honey tree, north of where you entered this area.
To the west of the Honey tree, there is a Super Repel.
Northwest of there, there is a hidden Potion, and north of that, you will find a couple of berry trees.
East of that, there is a Burn Heal.
To the north, you can battle Hiker Theodore, who has two level 15 Onix. You get 780 Pokédollars for winning.
West of there, you will find a Poison Barb.
If you go east and then north from there, you will find Wayward Cave.
Meet Dawn or Lucas
After you go south from Route 206 and enter Route 207, Dawn or Lucas will meet you and ask you to choose a hand. No matter which you choose, you get the Vs. Seeker, which lets you battle trainers again, then you get the Dowsing Machine, which will tell you if hidden items are nearby.
After this, the west path from Eterna City is no longer blocked.
Continue on to Route 207
After this, you can explore Route 207.