In modern usage, a landmark includes anything that is easily recognizable, such as a monument, building, or other structure. In American English it is the main term used to designate places that might be of interest to tourists due to notable physical features or historical significance. Landmarks in the British English sense are often used for casual navigation, such as giving directions. This is done in American English as well.
In urban studies as well as in geography, a landmark is furthermore defined as an external point of reference that helps orienting in a familiar or unfamiliar environment. Landmarks are often used in verbal route instructions and as such an object of study by linguists as well as in other fields of study.
A variant is a seamark or daymark, a structure usually built intentionally to aid sailors navigating featureless coasts. An example is the tower at Walton-on-the-Naze in England.
Here are some wallpaper collections of City Landmarks among the most popular in the world.