Mt. Coronet

Mt. Coronet is a massive mountain range which intersects at four different routes. It has numerous floors which require navigation from varying parts to get to your destination. To gain access to Route 216, you will need to enter through Route 211. However, if you wish to climb to the top of Mt. Coronet, you will have to enter through Routes 207 or 208. As you climb up, you will need most of the Hidden Moves and at one point in the game, you will encounter Team Galactic.
There are parts of the mountainside which are accessible when you've climbed high enough. These areas are snow covered. At the top of the mountain is the Spear Pillar. In Platinum, near the exit to Route 216, there is an extra area called the Iceberg Ruins where a Regice can be found if you bring in a special Regigigas

Evolution
Due to the special electromagnetic properties of this cave, if you level up a Magneton or Nosepass within the confines of the cave, they will be able to evolve.

Feebas:
Feebas can be found in the basement of Mt. Coronet where it is on 4 tiles which rotate each day. In addition to that, other Pokémon can be on that tile, but you can combine tiles with friends by Mixing Records.

Special Moves used in Mt. Coronet:
Surf
Strength
Defog
Rock Smash
Waterfall
Rock Climb
Flash