Stranger Suns — George Zebrowski

The orbiting tachyon detector was designed by physicist Juan Obrion to identify life in other star systems, but even though he expected to find some signs of life, he certainly didn't expect to find any life on Earth. When Obrion discovers that a culture has been concealed for many years far below Antarctica, he ventures out as part of a four-man team to explore the unknown. Juan, Lena, Malachi, and Magnus are awestruck when they discover a myriad of portals to parallel lands, but the maze they fall into makes them wonder if their journey will ever come to an end.