The Hotel Nakamura is where Carly, Sam Freddie, Spencer, and Mrs. Benson stayed while they were in Tokyo for the iWeb Awards in the episode iGo To Japan.
The iWeb Awards had provided all the nominees (including the iCarly team) a room with a double suit, a bathroom and space for storing their stuff.
While they were checking in, the clerk thought that Carly and Freddie were a couple who were checking in for their honeymoon, much to Freddie's delight, until Carly corrected her saying they were checking in for the iWeb Awards.
The clerk who checked them in (and thought Carly and Freddie were newlyweds).