More than 110,000 people logged onto the “Today” show Web site over the past few weeks to decide upon “Where in the World” they wanted to send Matt Lauer for his annual trek. And their choice, as revealed on Friday’s program? The Blue Lagoon in Iceland — though his “Today” cohorts Katie Couric, Ann Curry and Al Roker all guessed he was in Niagara Falls. That’s because he was surrounded by mist. In fact, he was sitting on a rock in 40-degree weather, while in a natural geothermal pool around him bathers waded in 100-degree water. Matt didn’t put on his swimming trunks.