The public is invited for a free tour of Great Falls Dam Powerhouse on April 8 to celebrate 100 years of operation. Guided tours will be given every 20 minutes from 10 a.m. to 2 p.m. Preregistration is required by visiting the Tennessee State Park’s Rock Island website and click on “upcoming events” to reserve a timeslot. Tour participants must register each individual in their party separately, including children.