Where is union cave in soul silver?

Union Cave is located in the Johto region of Pokémon SoulSilver, specifically in the western part of the Ecruteak City.

You can find it by following these steps:

1. Head to Ecruteak City.

2. Go west from the city's central plaza.

3. Follow the path along the river.

4. You'll find the entrance to Union Cave on your left side, near a bridge.

Good luck exploring Union Cave!