Could LIGO have detected R'lyeh if it existed? In Possible Bubbles of Spacetime Curvature in the South Pacific, that R'lyeh might be exist within a bubble of spacetime. (It appears to be a joke paper since some of the references are fictional, but the math appears quite serious.)
If a Bubble like the one described in the paper existed somewhere on (or in/near) the Earth, could LIGO have detected?
The reason I think LIGO might be able to detect it is because it can detect gravitational waves, and a spacetime bubble would presumably cause some "noise" in the signal. That being said, spacetime bubbles don't really change quickly, whereas LIGO is designed to detect speedy gravitational waves.
 A: The spacetime described in the paper is static, so it presumably does not generate any gravitational waves. LIGO does not detect static effects.
However, a kilometre-sized bubble presumably involves (negative) energy densities comparable to a solar mass (by analogy to the curvature induced in a black hole). That ought to have some effects on the outside since the edge has continuous derivatives. Presumably the edge effects falls off like some $1/r^3$ tidal effect. 
The GRACE pair of satellites can detect changes in ice sheet thickness and sea levels through gravity changes, so they might detect weird south pacific anomalies. Especially since it uses microwave beam to measure the distance between the satellites - presumably some residual curvature ought to affect the photons of the beam. 
Finally, a bubble would definitely bend neutrinos and gravity waves passing through. So maybe LIGO or IceCube can detect it that way, as an anomaly in detection from particular directions that move with the Earth. However, the angular resolution might not be enough for a small kilometre-sized entrance.  
