The Arboretum is a large room in the Chozo Ruins. The lowest part of the room is connected to the Arboretum Access and the Gathering Hall Access. The top of the room has a door with a Missile Shield which leads to the Sunchamber Lobby. There is a large central tree that goes to the top of the room. The lowest area has poisonous water with a number of platforms. One such platform has a patch of Venom Weed on it, along with a Runic Symbol. Reaper Vines line the walls of the lower level.
There is another Runic Symbol on the central tree above one of the branches that allows Samus to climb higher onto a walkway. This walkway goes past a number of War Wasp Hives that spawn War Wasps. The walkway goes through two Morph Ball tunnels, one of which has blocks destructible with the Morph Ball Bombs, the other with Venom Weed. Between the two tunnels, there is another Runic Symbol. At the end of the walkway is a ledge with a door that can only be opened by scanning all four Runic Symbols, the last of which is directly facing this door. The door leads to a Morph Ball tunnel blocked by a material vulnerable to the Morph Ball Bombs.