If you've wanted to explore Fort Knox at night, you may want to reserve your spot now.

It's shaping up to be a one of the biggest years for ghost tours at Fort Knox. Attendance has increased significantly as nearly all the tours have sold out this year. It's great news for the fort, as all the money from the tours go towards maintaining the historical site.

In a Facebook post by Fright at the Fort, Fort Knox's annual Halloween attraction, the only tour that still has openings is on October 6.

Paranormal investigators from 207 Paranormal will lead participants to the fort's ghostly hot spots, and provide all the ghost hunting equipment. All you need to bring is a flashlight, and your courage.

Tickets are $20 per-person, and non-refundable. Call 207-469-6553 to make your reservation.