Dunno if we have a Boundless thread here, so if we do and I have missed it, feel free to merge, mods.
Boundless is a buy to play sandbox building MMO where every structure is build by the players. The game is similar to Minecraft in how it works, but also significantly different. For example, each player gets a beacon and set amount of plots (that can be expanded later on as you level up) that has to be refueled (otherwise the structure will be destroyed over time due to world regeneration - any unoccupied chunks are slowly regenerated back to their original state). The game is surprisingly good, even if underappreciated and it really lets you unleash your inner dwarf, for example there's quite a depth for the crafting and forging system in the game, there are AOE tools that allow you to mine faster and there are so many materials, each in different colors that no two structures can really be the same (unless you actually try to copy someone else's build).
There's also a potential for mega structures, in fact there are several player-made cities in the game.
You can learn more and get the game at:
https://playboundless.com/ - it's available via Steam.