Large extra dimensions have been proposed as a possible solution to the hierarchy problem in physics .
One of the suggested models , the RS2 braneworld model , makes a prediction that black holes evaporate by Hawking radiation on a short timescale that depends on the black hole mass and on the asymptotic radius of curvature of the extra dimensions .
Thus the size of the extra dimensions can be constrained by astrophysical observations .
Here we point out that the black hole , recently discovered in a globular cluster in galaxy NGC 4472 , places the strongest constraint on the maximum size of the extra dimensions , L \lesssim 0.003 mm .
This black hole has the virtues of old age and relatively small mass .
The derived upper limit is within an order of magnitude of the absolute limit afforded by astrophysical observations of black holes .