From an AP report on the new audio tour at the Clinton Library in Little Rock, narrated by Bill Clinton:

Although Clinton says the Oval Office was "the best place in the world to work," he had another favorite spot in the White House: his private office. "I restored it to look the way it did after the Civil War, and I brought in a desk, which was Ulysses Grant's Cabinet table," Clinton says.

"And I would go in there, often after Hillary went to bed, or late at night, play my music, and that's where I did my reading and thinking and that's where my daughter would find me late at night when she called me from Stanford. I had a lot of happy times there."

And from the Starr Report:

According to Ms. Lewinsky, she and the President had ten sexual encounters, eight while she worked at the White House and two thereafter. The sexual encounters generally occurred in or near the private study off the Oval Office...

"Happy times," indeed.

A Little More Clinton At Clinton Library [AP]

Nature of President Clinton's Relationship with Monica Lewinsky [Starr Report]