Route 216 is the first area of the game to where you can catch your own Ice-type Pokémon. While Diamond and Pearl only had two you could find in the wild, Platinum has four in the regional Pokédex, though you won't find Swinub until the next route. Just remember like walking through the mud, you can't use your bike (and sometimes not your Running Shoes) in the snow. Also the areas where you walk will determine how fast you can move. Hail will be in effect in all snow areas and will damage all non-Ice type Pokémon, though Magic Guard, which Clefairy can use, is one of the few options to avoid weather damage.
You won't be able to face all the trainers right away or find all the items until after you come back with Rock Climb following your upcoming Gym match. The lone cabin in this route will have a bed for you to rest so it can serve as a place to fully heal your Pokémon team. Head north to reach Route 217
Route 217 will be difficult to navigate due to both the slow movement and heavy blizzard besides having to deal with Hail conditions in battle. Also there are ninja themed trainers hiding in the snow so look for mounds in the snow to find and face them. Use your Dowsing Machine to find hidden items while you are at it. When you arrive you'll encounter the Gym Leader Maylene who is traveling to Snowpoint City not properly dressed as a form of exercise. Out of all the items you can find as you are exploring the route make sure to go to the first house in the middle of the route to find HM08 (Rock Climb). You will still need the next Badge to use it outside of battle.
If you enter the house after collecting the HM, the person inside who owned the HM lets you keep it and also gives you the Icicle Plate. Right by the house in the northeastern section of the Route is the Icy Rock where if you level up Eevee around it, it will evolve into a Glaceon.
Follow the path in Acuity Lakefront to reach the Lake Acuity's entrance, and you'll see your rival Barry there. He tells you that to climb the slope that leads to Lake Acuity, you will need to win the Badge at the Snowpoint Gym. After he leaves, head east to Snowpoint City.
Snowpoint City has a few attractions, the main ones of interest to you on your first visit will be the Gym and possibly the Move Tutor.
Located in the upper right hand corner house is the Move Tutor where much like the one on Route 212 you can trade him shards in exchange for learning new moves if that Pokémon you want to teach it to is compatible.
In the upper left hand house is a girl who will trade a Haunter named Gaspar that will hold an Everstone (which prevents it from evolving into Gengar) in exchange for a Medicham.
There is also a ship harbor located in this city as well as a temple but you cannot use them until after you've defeated the Champion.
The secret to the puzzle of the Gym is to smash the snowballs on the ground is to slide in from above at a fast enough speed to smash them. Your main goal is that from the entrance, head straight to reach the Gym Leader, but only after you've smashed the snowballs that were in the way. Just slide around the Gym and predict which areas you need to slide down to smash those snowballs. Of course it will take some time to experiment until all the necessary snowballs are gone. You do not have to face all of the Gym Trainers in this Gym.
Once you've beaten Candice you will receive the Icicle Badge that will will allow you to use Rock Climb outside of battle as well as TM72 (Avalanche) that while it causes your Pokémon to usually move last, it's power will double if that Pokémon was struck by a damaging move first.
Now that this is over it is time to return to Acuity Lakefront.