Apollodorus is an impact crater on Mercury. Its unusual appearance, with radiating dark troughs, led to a nickname of "the Spider" by scientists before its official name was decided. Appolodorus is located near the center of Pantheon Fossae, which is a system of radial grabens situated in the inner part of the Caloris basin. The floor, rim and walls expose a low reflectance material excavated during the impact from beneath the light volcanic plains, which cover the central part of the Caloris. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Mercury they are named after deceased artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field and have been recognized as art historically significant figures for more than 50 years.
Image Source. Marker locations are approximate and may not always appear to align with image on map.