Sokka has to travel though a giant mountain full of tunnels with a bunch of nomads. She gets separated from her sister and worries. She also ends up having to sing to get some ferocious beasts to do what she wants. The whole time she tells herself that if she makes it through the tunnels, she'll end up in Omashu.
But in the end, even when she finally gets to see the city, it's just another bad thing. Omashu has been conquered by the Fire Nation.