The Route 32 side entrance to Union Cave in HeartGold and SoulSilver
Union Cave (Japanese: つながりのどうくつBond Cave) is a cave located in the Johto region. The main cave divides Route 32 from Route 33, though two other exits in the basement levels of the cave lead to the Ruins of Alph. A wildLapras can also be encountered deep in the cave every Friday after Morty has been defeated (as Surf is required to get to it).
Union Cave is a simple cave, with many pools of water. The main floor has two different ladders, both in the southern areaGSC and on opposite ends of the caveHGSS. The upper ladder leads to BF1, which, after crossing the pond, will lead to the Ruins of Alph. The lower ladder leads to a small hallway, which also has a pond, and the ladder to BF2. The lowest level of the cave has several ponds, the southern-most containing, on Fridays, a Lapras.
Union Cave in Pokémon Gold and Silver: The Golden Boys
In the Pokémon Adventures manga
Union Cave appeared in Off Course with Corsola, where Crystal was traveling through the cave to get to the western part of Johto. While going through the cave, she noticed a Magneton, which was not native to the area. She was then attacked by a group of Magneton, all of which belonged to Lt. Surge, who had ordered them to catch any wild Pokémon passing by. When the Gym Leader himself arrived, he saw that his Poké Ball trap hadn't caught anything, leading him to believe that the commotion was just a false alarm. He then proceeded to exit the cave through an underwater tunnel, not noticing that his Magneton had dropped the unconscious Crystal into his submarine.
In the Pokémon Gold and Silver: The Golden Boys manga
Union Cave appeared in Escape from Magma!? of Pokémon Pocket Monsters. Red and his Pokémon went there by traveling on a Lapras. Inside, Giovanni and some Team Rocket Grunts took over the cave by building an amusement park. As Red and his Pokémon went in, it turned out to be a trap as Giovanni sealed the entrance. The group managed to escape when Clefairy's digger drill dug a hole. However, it took them deeper in the cave where Giovanni found them and summoned his Slugma from a lava pit.