One of the Deep Blue Structures from Katters Structures.
The Deep Blue Labs are mostly underground structures with only a copper door visible on the surface.
In the Center is a destroyed version of a Deep Blue Portal.
The main blocks are:
Chests contain most of the Blocks needed to construct a Deep Blue Portal.
A Lectern contains one of two books explaining how to enter the Deep Blue.
Deep Blue Labs, will naturally spawn in Overworld Grassland Biomes.