Gameboy: Gold/Silver: Ice Path

Icy Mazes

The Ice Path shouldn't be too hard to get through. If you are stuck, the Map has red arrows that'll tell you where you need to go.

You'll find some new Pokemon in here, a small mammoth like thing called Swinub. There's also a shy bird called Delibird in the Silver version.

HM07 - Waterfall
You can find the last HM, HM07 in the Ice Path. This HM lets you ride up waterfalls.