From the outside, Turnbull Manor at the corner of Kennesaw and Maple avenues looks just like any of the other grand old mansions that line the streets of the Northwest Marietta Historic District.
But underneath its ornate facade and oak-shaded lawn lies a forgotten underground tunnel with a mysterious past.
Jim Trimble — who owns the house with his wife, Robin Trimble — said they discovered the tunnel in 2016 while renovating to prepare for the Marietta Pilgrimage Home Tour, which invites the public to walk through historic homes in the area…