Ancient Brick is a block from the Dungeon of Arcana. It is a detailed blue brick that seems to have come from ruins.
Like all other Arcana structure blocks, Ancient Brick is indestructible and is only obtainable with Creative mode, cheats, or another mod.
Locations and Obtaining
As Ancient Bricks are indestructible, they cannot be obtained in normal Survival gameplay.
Ancient Bricks can be found in most (if not all) rooms in the Dungeon of Arcana alongside other indestructible blocks and locked doors.
Before v1.4.0, there was a bug that made these blocks have weak blast resistance despite being indestructible, so they could be blown up (and would sometimes drop). However, this bug was fixed as of v1.4.0.
If obtained, Ancient Bricks can be used as decoration or as an aesthetic replacement for Bedrock.