Analytic approximation to 5 dimensional Black Holes with one compact   dimension
  We study black hole solutions in $R^4\times S^1$ space, using an expansion to fourth order in the ratio of the radius of the horizon, $\mu$, and the circumference of the compact dimension, $L$. A study of geometric and thermodynamic properties indicates that the black hole fills the space in the compact dimension at $\epsilon(\mu/L)^2\simeq0.1$. At the same value of $\epsilon$ the entropies of the uniform black string and of the black hole are approximately equal. 
D. Karasik, C. Sahabandu, P. Suranyi, L.C.R. Wijewardhana