Getting to the cave wasn't easy.Peter and the ohers trekked for eight hours through thick jungle to get to the cave's enirance.Then they went into the cave.They worked undergrond for twelve days, following the son Trach river through the cave.Petet made careful measurements so that he could draw accurate maps later.Finally, they came to the cave'sexit.Peter was very excited.he has discovered that the son Trach river was 11 kilometres long-the longest underground river in the world.