There are loads of places to visit
Lincoln, about 40 minutes from Louth has the Cathedral, Castle, Brayford Pool, Etc, Etc.
Louth itself is scenic with nice church, lots of old buildings, Etc.
Boston also has an impressive church, locally known as the stump.
As previously said Donna Nook, along with Gibralter Point nr Skegness for bird watching, along with lots of smaller reserves littered along the coastal area.
You are on the edge of the wolds at Louth and several places worth visiting would be Horncastle, Harrington, Somersby (Tennyson's birthplace), Little Cawthorpe, just to name a few.
Hope this helps you.