Yes, individuals who have traveled around the world can observe several visible phenomena that support the notion that our planet is round or spherical. Here are a few examples:
Horizon curvature: As someone travels across large bodies of water or observes distant landscapes from high elevations, they can notice the curvature of the Earth. The horizon appears to curve away from the observer, and the degree of curvature increases with altitude.
Circumnavigation: People who have circumnavigated the Earth by traveling in one continuous direction eventually end up at their starting point. This is possible because the Earth is a sphere, and traveling in a straight line would eventually lead back to the starting point.
Time zone differences: Traveling across longitudes results in encountering different time zones. The fact that time zones exist and vary based on longitude is due to the Earth's rotation on its axis, which is easier to comprehend when visualizing a spherical planet.
Flight paths: When flying long distances, especially over the poles, the flight paths follow curved trajectories known as great circle routes. These routes are the shortest distance between two points on a sphere and reflect the spherical nature of the Earth.
Satellite imagery: Images taken from space by satellites and spacecraft clearly show the Earth as a round object. Numerous photographs and videos taken from space provide undeniable visual evidence of Earth's spherical shape.
These observations, along with scientific measurements and extensive astronomical and geodetic research, confirm that the Earth is indeed a spherical object. It is important to note that the notion of a round Earth has been established for centuries through a combination of scientific study, observation, and evidence from various fields of research.