Ijams Nature Center is one of Knoxville's best escapes because it does not ask you to leave the city behind. Within a short drive of downtown, trails thread through forest, wetlands, river bluffs, and old quarry ground that has been folded into the wider Knoxville Urban Wilderness.
Come for a walk rather than a formal museum visit. The boardwalks and river overlooks are easygoing, while the quarry and longer trail connections can turn it into a proper half-day outdoors. It is especially good if you need fresh air between downtown, the university, and the Great Smoky Mountains.