I grew up in Chattanooga (went to high school with BW1stpar)
The Tennessee Aquarium is nice. Fresh water and salt water fish.
If you have young kids, the Creative Discovery Museum offers hands on fun learning.
Rock City up on lookout mountain
Incline Railway (goes Straight UP lookout mtn.)
TN River walk / Coolidge Park / Walnut Street pedestrian bridge (all tied together along TN river)
Murder Mystery dinner theater shows are a hoot
The Choo--Choo? Its mainly a hotel with a train and railcars on static display. But they do have sleeping cars you can rent overnight. Station House Cafe for dinner where the waiters & waitresses sing up on stage. Then breakfast in the hotel's restaurant. Bands play concerts @ Track 29.
Tennessee Valley railroad museum has different length rides you can take on vintage trains.
There's lots more, but that's my starter list for ya. Welcome to Chattanooga!