 One side of the original, central castle was protected from invaders by natural means, utilizing the impassably steep slope of the mountain; two stone castle gates afforded other protection to the castle and the homes that were built within its walls, dug into the slides of the mountain and giving out through front entrances facing on narrow, twisting, steep stone alleys.Its location surrounded by the Apennines would have prevented Barrea's development into an industrial area had not other economic obstacles also existed; historically, residents existed by tending small farms in plots on the mountainside.A major emigration took place after the earthquake of 1984, when many residents declined to return to the homes that were ruined in the tremor.