This is probably way more information than you ever want to know, but my Dad was a surveyor for our local power company so we always made a habit of looking for the markers.
There are several customized and unique land survey markers around the world, but some of the most interesting and sought-after monuments for land survey buffs to observe are the Walt Disney survey markers. They have established unique designs for both Disney World and Disneyland.
The Disney World cap has a mickey mouse symbol with latitude and longitude lines running over the head which represents the earth. The center of the latitude/longitude lines marks the exact center of the disc, which actually has a purpose: surveyors use that center point to place their receiver antenna for a known position when conducting a survey. Another fun fact: for many years, the top of the Cinderella Castle was used as a triangulation point. It worked great because it could be seen from all directions, and it had an established location and elevation.
Whether Disney is building a brand new hotel, restaurant, or thrill ride, each development project begins and ends with a survey of the land. Therefore, these markers serve a very important purpose in the development and management of the parks today. Disney maintains a staff of about 20 people in the surveying department who use these survey markers, along with GPS, GIS, and AutoCad to map out the utilities and other infrastructure in the parks.
Not only are the Disney land survey markers crucial to the development of the park, they are also fun for visitors to find! The typical Disney visitor would probably not even notice these tiny landmarks hidden right under their feet. Some Disney enthusiasts track and log the location of these survey makers throughout the Disney parks, and have established websites to catalog them and help visitors find them.