Otto Lidenbrock finds an old journal with instructions on how to get to the center of the Earth and follows them, facing and overcoming many dangers but not actually getting to the center.
One of the significant events is when the scientist Otto Lidenbrock discovers a coded journal left by Arne Saknussemm, who wrote it during the fifteen hundreds. Otto’s assistant Axel decodes the journal and learns of a secret passageway to the center of the Earth, deep into the Earth’s core.
Otto hires a guide, Hans. They follow Saknussemm’s directions, and begin at a crater on Mount Sneffels. The journey is more treacherous than they expected.
"…There are about three hundred volcanoes on the whole surface of the globe—but the greater number are extinct. Of these Sneffels is one. No eruption has occurred since 1219—in fact it has ceased to be a volcano at all." (Ch. 4)
Although Saknussemm is a heretic and an alchemist, he seems to have known what he was talking about. The team is able to follow the directions and tunnel into the earth.
As far as we had hitherto gone, facts had proved the theories of Davy and of Lidenbrock to be correct. Until now, all the peculiar conditions of refractory rocks, of electricity, of magnetism, had modified the general laws of nature, and had created for us a moderate temperature… (Ch. 41)
Inside of the Earth they face treacherous winds, and when they finally get outside they barely escape with their lives. Although they only went inside a volcano, their feat is still celebrated and revered. Axel decides to write about the journey, which is the manuscript you read as Journey to the Centre of the Earth.
The major complication might be that the team never really made it to the center of the Earth, so to speak. However, they did make it deep into the Earth, into the crater or the volcano. They faced danger and treachery at every turn, and came out alive and celebrated.
When they find the journal that tells them how to get to the center of the earth and how they escape