Topic: Go Vacation! Wii - underground city

Hi everyone! I'm new on this Nintendo forum but I play wii and Nintendo for many years.
I started playing "Go Vacation!" on Wii many years ago and I have a big doubt about it.
When you play Go Vacation on Wii, you can find some balloons in different places. Inside it, there are secret messages to help you discover new places on the map and do other things. You can see all the messages that you find, in the menu of Go Vacation.
So, I found one message in a balloon in the Snow Resort that said something like "Here in the Snow Resort, it has just been built a new underground city, if you search well, you can find it somewhere..."
My doubt is, basically: where can i find the city? What should I do? Has someone ever entered it?
I want to specify that I don't think it could be the underground cave in the Snow Resort with lava, colored mushrooms and crystals, if you know what I mean.
Thanks everyone for the help and sorry for the non-perfect English but I'm from Italy

It was Lava Cave in Snow Resort.

Oh ok, thank you so much!!
I'm just a bit confused because a tik should appear next to the message, indicating that you have completed the goal, but it does't appear for me, in the message of the underground city, idk...