Bill Lichtenstein is proud to show off his large new broadcasting complex, which includes a radio studio, concert stage and listening room.

None of it actually exists, however, but instead occupies space inside a virtual online world known as "Second Life." 

More than 900,000 people have entered this world since it opened in 2003, and many, such as Lichtenstein, have built their own structures inside it.

"It's not gaming, it's not a Web site," said Lichtenstein, of Boston. "It really is a chance to experience a new culture and new place and new people."

Lichtenstein, president of Cambridge-based Lichtenstein Creative Media, has held live radio shows and company meetings at his virtual complex, and offered the first concert inside Second Life in August.