Old foreign animated movie about volcano!


A long time ago I watched an animated movie about people who lived under the volcano and they wanted to go to the surface.
The two main characters are the little girl and boy and their grandma.
They are chased by rats who are trying to stop them.
At some point the grandma dies and they are left alone. They find way out but before they are able to get to the surface they have to face this huge dragon.
At the end, they succeed and are among the flowers and go swimming in the sea.
Now, the movie is very old, animated and foreign (I don't know from which country).
And I've been searching for ot for years.
In the title was the name paradise or heaven or something like that.
And yes, the people in the cartoon were almost naked (if that rings a bell xD).
Thank you very much for any help!