Cruise ships usually sail regularly or irregularly along certain water tourist routes and stop at one or several tourist spots for tourists to visit. Ordinary passenger ships can be called cruise ships if they are used for tourism or modified for tourism. After 1960s and 1970s, with the development of tourism, more and more cruise ships were specially designed and built for sightseeing. In addition to the basic functions of ordinary passenger ships, most of these cruise ships provide special sightseeing and entertainment facilities and services. (In this picture, there is a carnival cruise ship with a red wing on the upper part, next to the Royal Caribbean cruise ship. )