Mt. Silver is the point between Kanto and Johto.It is where the Famous battle between Red and Ethan took place.It is the Tallest mountain in the Indigo Plateau and Maybe the whole Nation though this is unlikely.It is very cold near the top and has a great view.It is the home of the secret Light Alliance base.Many Rare pokemon can be found here and so can a Legendary from time to time.Many trainers try to hike it but usually stop at the 3rd level.There is a small encampment near the top where Red used to live.Gray now uses this encampment from time to time.To gain access you need to beat both the Kanto and Johto Leagues.