For a city with under a million people, Columbia has a surprisingly large amount of space dedicated to parks.
Congaree National Park

Columbia sits just outside one of America’s 62 esteemed National Parks. This park preserves one of the last “old growth bottomland hardwood forests” in the country. It’s a small park but has a really nice boardwalk trail that winds above the marshy land and a few at ground level. My personal highlight is that the park is free! For a complete guide to the national park, look no further.
Congaree Creek Heritage Preserve

When I was at this preserve, I saw one of the largest alligators ever! The park is just a few miles outside of town, easily accessible on Interstate 77. It sits along the Congaree River and even runs beside to it for a bit. The nature loop is just under three miles. It starts as a questionable suburban sidewalk before you’re transported into the thick woods. Be on the lookout for gators lounging along the shore:

Finlay Park

What this park lacks in size is compensated with stunning views of the Columbia skyline. Centered around a small lake, the urban park sits on a hill overlooking itself. The two levels are connected by stairs adorned with cascading waterfalls. At the top is a pretty impressive fountain that spits water everywhere. The lower is grassy and flat with some benches. The upper portion is also a few blocks from the governor’s mansion.
Columbia Canal and Riverfront Park/Three Rivers Greenway

This four mile trail is on an island between the Congaree River and the Columbia Canal. The short-lived canal was overtaken by the railroads in the 19th Century, but now plays home to the flat and scenic trail. Being just outside of downtown, there is a small parking area, restrooms and a steep path from the parking lot down to the river.
Cayce Riverwalk

This monster of a trail is on the west side of the Congaree River and runs for 12 miles. Along the way are a number of scenic overlooks of the river. The trail passes through a number of other parks on this list, including the Canal Trail and the Congaree Creek Heritage Preserve.
Lake Murray
I haven’t been to this park, but it’d feel wrong to exclude it. A lot of the lakeshore is residential, but Dreher Island State Park and Lake Murray Public Park give the public access to the lake. Neither of the parks have extensive amenities, but the former has a few trails and access to 12 miles of the lakeshore. The park’s spread across three islands and is popular for fishing, they claim to have some of the best bass fishing in the area.

Sesquicentennial State Park
Affectionately known as ‘Sesqui’ by the locals, the state park acts as Columbia’s largest city park. The 1,400 acres are just outside of downtown. The centerpiece of the park is an ornate lake with a number of trails branching from it. Jackson Creek runs north to south through the park, essentially cutting it in half. There is a splash pad, a dog park, hiking trails and 12 miles of hiking trains. Do however note that the park costs $6 a person for entry.