Indigo Plateau is home to the Kanto and JohtoPokémon League There is no items here. The closest town/city to it is Viridian City and New Bark Town. The Elite Four can only be accessed by traveling through the cave at the base of the plateau which is protected by eight Kanto and Johto Pokémon League Guards that check trainers for all eight Kanto and Johto Pokémon Badges before allowing them to advance towards the Plateau's cave entrance.
Landscape Differences from Red, Blue, and Yellow to Gold and Silver
In the original Pokémon Red and Blue as well as Yellow Version, the grounds of the Indigo Plateau was surrounded by a series of citadel walls. The fortifications consisted of five outer reinforced walls, five walls within a moat, and three individual barriers. Each defense line was protected by one of eight elite Indigo Plateau guards dressed in black armor. In addition, beyond the final wall was a cave filled with strategically placed boulders that blocked the path to the stadium housing the Elite Four as well as a series of boulders outside the stadiums entrance.
However, in Pokémon Gold and Silver, the grounds surrounding the Plateau drastically change. The fortifications previously mentioned to have existed in the original games no longer exist. Remnants of the path and its fortifications are still being visible such as the moat which has been reduced to a small pond. In addition, stationary boulders are now located where the walls onces stood with the garden near the Reception Room being replaced by a series of ledges. It is assumed that the plateau experienced a rock slide or earthquake during the two year gap between the games that drastically altered the plateaus landscape. In addition, the Reception Room building now contains a checkpoint as well as a path to Mt. Silver and a path to the rest of the Kanto region.