The name suggests a place where people pay money to suffer on treadmills. This is not that. The big gym is a large, rusty-brown mushroom. It grows in impressive clusters on stumps and dead wood. The cap measures five to fifteen centimetres across. It is covered in fine, scaly fibres that give it a textured appearance. The colour ranges from rusty orange to brownish-yellow. It fades with age. It looks assembled from spare parts that nearly fit. The gills are crowded. They are yellow when young, turning rusty-brown as the spores mature. The stalk is five to fifteen centimetres tall. It often has a skirt-like ring near the top. Below the ring, the stalk is covered in dark fibres. The spore print is a distinctive rusty brown. Take a spore print. That is how you know. Certainty is rare. This offers some. This fungus is a saprotroph. It feeds on dead wood of both native and introduced trees. It breaks down tough lignin and cellulose. It turns fallen logs into soil. It often appears in large clusters. Sometimes there are dozens of mushrooms on a single stump. It is a demolition crew that works in silence. The work is slow but thorough. The big gym is bitter and inedible. Some species of Gymnopilus contain psychoactive compounds. This species is not typically used for such purposes. The name junonius refers to Juno, the Roman goddess. It perhaps alludes to its stately appearance. A mushroom named for a goddess. A mushroom that tastes like regret. The contrast is sharp. In New Zealand forests, the big gym is common on dead wood. It can be found in native bush and pine plantations alike. The rusty-brown spore print is a key identifying feature. It distinguishes this species from similar-looking but edible varieties. Mistakes here are unpleasant. The bitterness serves as a warning. Walk past a stump in a damp forest. Look down. There they are, dozens of them, rusty-brown and clustered. They are eating the dead wood from the inside out. No treadmills. No monthly fees. Just a fungus doing its job. The efficiency is notable. It requires no encouragement. And that seems to be enough for a mushroom named after a goddess. It carries on. The clusters form. The wood decays. The cycle continues without fanfare. The big gym does not seek attention. It seeks substrate. It finds it. The name remains a joke. The fungus remains a fungus. No one told it otherwise.