I don't think they have ever been to:

Peru
Poland
Iceland

Maybe they have and I can't remember, but it think it would be interesting.
In Peru they could have to find a certain block at Machu Picchu since some of them are numbered when they are rebuilt.

In Poland they could have to go to the Salt Mine in Krakow.

This show is awesome... but am having a hard time trying to find a favorite team this time. Definitely not Team Blue Lagoon though!!!