Eterna City is the bicycling capitol of Sinnoh and the location of the second Gym Leader, Gardenia. It also has a Statue of Dialga/Palkia. Team Galactic has a base here as well.
What's going on?
When you enter town, a fresh face, Cynthia, will meet you outside the Galactic Building and hand you HM01 Cut. Head down and enter the bike shop to discover that it's clerk, Rad Rickshaw, is not there. Talk to the boy at the table, and he will tell you that the manager went off to the Galactic Building and hasn't returned. The thing is, the Galactic Building is barricaded by trees that need to be cut down, and you can't use Cut until you get another Gym badge. Sounds like now you need to take a visit to Gym #2.
Exploring the city
In the city you can pick up another Pokétch app, learn about the underground, rename your Pokémon, get a bike and in Platinum you will get your first egg.
Pokémon Center
Speak to a woman in the Pokémon Center to receive the Friendship Checker app for your Pokétch. This app will have your party's Pokémon and when clicked on it will show you how happy they are.
Underground man's house
Next the Pokémon Center, you will find the Underground Man who will give you an Explorer's Kit and he will give you a tutorial and have side quests for you to get items to use in the Underground.
The Underground is also the place to get ancient Pokémon fossils.
Poké Mart
| Poké Mart | |
|---|---|
| Right cashier | |
| Poké Ball |  200 |
| Potion | 300 |
| Super Potion | 700 |
| Antidote | 100 |
| Paralyze Heal | |
| Burn Heal | 250 |
| Ice Heal | 250 |
| Escape Rope | 550 |
| Repel | 350 |
| Left cashier | |
| Heal Ball | 300 |
| Net Ball | 1,000 |
| Nest Ball | 1,000 |
Eterna City Condominiums
Next to the Poké Mart there are the Eterna City Condominiums, and on the ground floor you will find the Name Rater who will rate and also rename your Pokémon if you want to. There is also a boy who will trade you his Chatot for a Buizel.
On the second floor, speak to an old woman to obtain TM67 Recycle.
Mystery House
At the southern end of town, you will find an empty house next to the gym. Return later on, after you have the National Dex and met Professor Oak in Pal Park, to find that Oak has returned, and he will hand you an Up-Grade .
Head into the exit building down to the south to find one of Professor Rowan's assistant, who, if you have met 35 Pokémon, will reward you with the Exp. Share.
Togepi egg
In Platinum, if you make space in your party before you get your bike from the shop, Cynthia will give you an egg containting Togepi, which will hatch after the required number of steps
Herb Shop
This shop, located to the right of the Team Galactic Building, sells herbal medicine. It is cheaper than the Poké Mart equivalent, but its bitter taste makes Pokémon dislike you for feeding it to them.
- Energypowder:
500 - Energy Root: 800
- Heal Powder: 450
- Revival Herb: 2800
Legendary Pokémon statue
Next to the Herb Shop is a statue of Dialga/Palkia which depends on the game you are playing. A tile right behind the statue has a hidden Draco Plate
Item
- Draco plate (hidden) - right behind statue
Forest badge
The Eterna City Gym is a grass type gym. It can be very confusing at first. You must locate and battle every trainer in the gym in able to challenge Gardenia herself. You will find the first trainer in the upper left-hand corner. Once you have defeated him, he will reveal a clue to where you will find the next trainer. This will continue on until you defeat all four trainers. Gardenia will be devastating to those who chose Piplup, very difficult for those who chose Turtwig and of low difficulty for those fortunate enough to select Chimchar. For those with Piplup and Turtwig, you will be able to catch the only other Fire-Type available in the game, Ponyta, to the east on Route 211 or you can catch a Starly and train it to level 9 so it learns wing attack as grass types are also weak against flying type moves.
Trainers
| Diamond and Pearl | |
|---|---|
| Trainer | Pokemon |
 Lass Caroline Reward: 240 |
|
 Aroma Lady Jenna Reward: 489 |
|
Aroma Lady Angela Reward: 544 |
|
 Beauty Angela Reward: 544 |
|
Gym leader battle
| Diamond and Pearl | |
|---|---|
| Trainer | Pokemon |
 Leader Gardenia Reward: 2640TM86 Grass Knot Forest Badge |
|
With the Forest Badge in hand, you can now use Cut outside of battle and also any traded Pokémon will now obey up to lvl 30
Items
- Super Potion - in tree line behind gym
Team Galactic Building
With Cut in hand, head over to the Team Galactic Building and hack down the trees to get to the entrance. As you ascend to your destination, you will be fight in a few battles with Galactic Grunts. Once you have reached the fourth floor, speak to Galactic Commander Jupiter, and prepare for battle. With Jupiter's defeat, Rad Rickshaw will be freed. Return to his shop afterwards to receive a brand spanking new Bicycle. Head to Route 206 to resume your journey
Items
- TM46 Thief
Trainers 1F
| Diamond and Pearl | |
|---|---|
| Trainer | Pokemon |
 Galactic Grunt Reward: 520Potential Double Battle with below grunt |
|
 Galactic Grunt Reward: 540Potential Double Battle with above grunt |
|
Trainers 2F
| Diamond and Pearl | |
|---|---|
| Trainer | Pokemon |
Galactic Grunt Reward: 520 |
|
Galactic Grunt Reward: 600 |
|
Trainers 3F
| Diamond and Pearl | |
|---|---|
| Trainer | Pokemon |
Galactic Grunt Reward: 480 |
|
 Scientist Travon Reward: 720 |
|
Commander Jupiter on 4F
| Diamond and Pearl | |
|---|---|
| Trainer | Pokemon |
 Commander Jupiter Reward: 1600 |
|
Item
- PP Up (hidden, DP, requires Surf) - northeast corner
- Moon Stone (Platinum, requires Surf) - northeast corner