Interaction between the wakes of two cylinders in side-by-side configuration creates interesting flow phenomena. The nature of the wake depends on the Reynolds number and the transverse pitch distance between the cylinders. The flow over two side-by-side cylinders of equal diameter is simulated in 3D at Reynolds number 5000 using Large Eddy Simulation (LES). The centre-to-centre transverse pitch ratio is varied and the flow behind the cylinders is classified into either a bi-stable flow regime with biased gap flow or a regime with parallel vortex streets. Furthermore, representative instantaneous flow fields, Strouhal number and the time varying drag coefficient C′D are presented.