The task of multiple, physically-separated mobile robots meeting at a point is considered in this paper. This task, termed as rendezvous, is studied when the mobile robots have unequal speeds. An algorithm for computing the minimum time rendezvous point (denoted by P*) for a pair of robots moving amidst polygonal obstacles is presented. The algorithm is based on the notion of visibility graph and computes P* exactly. Comparisons with an alternate approach based on level sets are given. An extension to rendezvous of three robots (in minimum time), based on the notion of Apollonius circles is also presented. An experimental setup consisting of multiple mobile robots, fabricated in-house, is described. Experiments with the robots confirm the efficacy of the proposed algorithms.