1&1 Internet is one of the world's largest web hosting companies. The company is based in Germany (its parent is United Internet), but also has significant operations in the U.S. and United Kingdom. A key hub in the company's American operations is its 54,000 square foot data center in Lenexa, Kansas, which houses 860 racks. Information Week recently had a look inside the 1&1 Lenexa facility, and has published a slideshow of 13 data center photos.
The 1&1 Internet facility is also the "mystery data center" featured in our Name That Data Center contest. Congrats to Chris, who made the connection in the comments.