In Pokemon Silver, you can access Mt. Mortar which is a similar mountainous location. Here's how to get there:
1. Beat the Elite Four: First, you need to defeat the Elite Four and become the Champion of Johto.
2. Head to Ecruteak City: Once you're the Champion, head to Ecruteak City.
3. Go North: Follow the path north of Ecruteak City, heading towards the mountains. You'll eventually reach Mt. Mortar.
If you're playing Pokemon Crystal, then getting to Silver Mountain is a bit different:
1. Reach Ecruteak City: After leaving the Goldenrod City Gym, head east to Ecruteak City.
2. Speak to the Old Man: Speak to the old man in front of the Burned Tower. He'll give you a key to enter the tower.
3. Enter the Burned Tower: Go inside the Burned Tower, which is now accessible.
4. Battle the Team Rocket Grunts: Battle your way through Team Rocket Grunts and eventually encounter the legendary Pokemon, Entei.
5. Enter Silver Mountain: Once you defeat Entei, you'll gain access to Silver Mountain, a location just north of the Burned Tower.
Let me know if you have any more questions about Pokemon Silver or Crystal!