Alafia River State Park, Mountain biking trails and natural park in central Florida, US.

Alafia River State Park is a Florida State Park near Picnic in Hillsborough County, 17 miles southeast of Tampa on County Road 39. Its terrain was excavated by draglines during phosphate mining, and some mined features such as the Old Agrico Pits remain, while others were shaped into small lakes. The park has 17 miles of bike trails, ranging from novice to highly advanced sections.

The site operated as a phosphate mining area under American Cyanamid until 1996, when Cytec Industries donated the land to Florida authorities. This donation transformed the former industrial site into a public recreation area.

The park's mountain bike trails were first built and kept up by the SouthWest Association of Mountain Bike Pedalers (SWAMP); the Friends of Alafia now maintain them. Riders can spot a cypress draped with gray Spanish moss along the riverbanks, and kayakers share the dark water below.

The park is open daily from 8 AM until sunset with a vehicle entry fee of $5 at the South County Road 39 entrance near Lithia. Visitors should plan for the terrain's elevation changes, which differ from typical flat Florida landscapes and require appropriate footwear and conditioning.

The park's advanced mountain bike trails run through the Old Agrico Pits, former phosphate excavations that reclamation left as persistent terrain features. Brewster Phosphates shaped some pits into small lakes under Florida's Old Lands Program, which the state later deemed a failure.