Minecraft Authentic Adventure (latest version: 1.3.4) is a minimalistic mod for 1.2.5 that reverts the game to a more Beta-esque aesthetic with hilly terrain generation, sandbox gameplay and an overall enjoyable experience for player from both the golden age and the modern era.

Why don't you check out Authentic Adventure's sister project, Minecraft Diverge?

Features

• Overhauled world generation, making it more hilly and Beta-esque
• Plenty of customisation options for world generation, gameplay and visuals to fine tune your experience
• Reworked hunger system and new classic mode
• Added extra challenge to Hardcore mode alongside extra benefits
• Improved lighting engine
• A few new items and enchantments

Trailer for 1.0 (Youtube)

Screenshots