Lower Broad:Tootsie's Orchid Lounge, Ernest Tubb Record Shop, Robert's Western World,etc
The Ryman Auditorium-- The mother church of country music
Opryland Hotel and Conv. Center-- extravagance. With a running river , waterfalls and indoor gardens
The new Schermerhorn Symphony Hall-- The new home of the Nashville Symphony.
Fort Nashborough-- Located on the Cumberland River right off of Lower Broad.
The Parthenon at Centennial Park-- built as a part of Tennessee's 100th anniversary of statehood.
Several Civil War Sites--
The Gibson Guitar Factory-- Free tours, but reservations are required.
Germantown-- Oktoberfest (since I think you're planning an October trip). They have beer.
Smokie mountains