If you like maps which come in a series and tell a story, you might like Forgotten Blocks map, which is actually the map that comes after The Different Elements. You could play the initial map first if you prefer, but then again Forgotten Blocks map does fine as a standalone experience as well. This map is a significant improvement over the first map in the series in terms of building design, redstone circuitry, and object placement. However, there is a common theme from the first map which is found here as well. In order to win, you’ll need to complete 20 different blocks.
If you’re looking for a decent sized adventure map to keep you busy for a few hours, then the Forgotten Blocks map would be perfect for you. It’s not too long and it’s not too short, so you could probably play through it in a single go as well. There is a surprising number of special commands hidden in command blocks throughout the map too. These allow for many new experiences without the use of any mods, but those won’t be spoiled here. Since the map is worth playing through if you want to know what it contains, go have a look.