im not completely positive but i was told theres a door in the game corner and you use the key to open it. however there is a man blocking the way and i have no idea how to move him
use the basement key in goldenrod city. the key is in goldenrod.
goldenrod city
Hit switches 3, then 2, then 1.
you get the card key for the radio tower in goldenrod by saving the director from the underground basement. Talk to him and he should give it to you.
In Pokémon HeartGold and SoulSilver, you can find Lance in Goldenrod City at the Goldenrod Department Store. He appears in the basement after you defeat Team Rocket and complete the events in the Radio Tower. Look for him near the entrance of the basement area, where he will help you confront Team Rocket. Afterward, he will also challenge you to a battle.
All you have to do is defeat the Mahogany leader and reach the top of Radio Tower in Goldenrod city.
In Pokémon Gold, Silver, and Crystal, the key for the Goldenrod City Underground is found in the Goldenrod Department Store. You need to go to the store's basement, where you will encounter Team Rocket. Defeating the Team Rocket members will allow you to obtain the key, which you then use to access the underground area.
Actually its 3,,2,1 and u get it all unlocked
In the basement under Goldenrod city mart when Team Rockets invade the radio tower.
you battle him
In Goldenrod city
It's in Goldenrod City. Across the train tracks, & to the left, the building on the far left will show you the stair case to the "basement". Go down a bit, & the skinny hallway on the right will lead you to the room you need to unlock with the Basement card/key.