Wuh's up?

The grandchildren & their parents were on vacation this week. Tuesday afternoon, my cell phone rang--it was D.
"Bubbie, guess where we are!" he exclaimed. I knew where they were, but I played along.
"7-11?" No. "A restaurant?" No. "The park?" No. "The museum?" No.
"OK, give me a hint," I said.
D answered, "It starts with a "wuh."
"A 'wuh'?" I asked him, wondering what on earth a "wuh" could be. "Hmmm- I give up," I said.
"Wuh-sconsin!" he yelled happily.