This paper proposes an algorithm to change the concept of rendezvous points (RPs), which have been commonly used in mobile sink routing problem of wireless sensor networks (WSNs) to rendezvous areas (RAs) and to generate RAs by using geographic information system (GIS) tools. With the traditional RPs, a mobile sink must have visited the points, and possible deviations from the points would cause the mobile sink difficulty finding exact locations to collect data. However, with suggested RAs, the mobile sink is capable of receiving data from sensor nodes in an RA by visiting any points within the RA. It also reduces the traveling distance of the mobile sink, thereby prolonging its lifetime. With appropriate extensions with GIS tools, the algorithm can generate 3D RAs, which can be simulated in more realistic environments.