The Third Tunnel 3/4 mile long tunnel on the west end of the Elroy-Sparta State Bike Trail in Wisconsin. This trail links with the La Crosse River State Trail and then to the Great River Trail in Onalaska. On the east end it is linked with the 400 trail from Elroy to Reedsburg. The base is crushed limestone with no more than 3 % grade.
This trail was the first in the Rail-Trail Conversion in 1967 when the Wisconsin Conservation Service purchased the right of way.