Melbourne's mild weather makes it an ideal shoulder-season destination. June and July are the coolest months; November and December are the wettest. Melbourne Airport, also known as Tullamarine Airport, receives international flights and is the point of entry for most visitors. American citizens are required to have a passport and visa to enter Australia. Set on Port Phillip Bay and bisected by the Yarra River, Melbourne is compact and easily navigable. The CBD is laid out in a grid, which makes exploring by foot easy. The city's tram system is the biggest in the world, so no car is needed here. Tipping isn't standard in Australia, but a 10 percent gratuity is a nice way to reward good service. Electricity is 240 volts and plugs are Type I.