The noun splendor refers to something that is magnificent or grand. If your prom was held in a luxurious ballroom with elegant decor, you might note the splendor of the setting.
The noun splendor has its roots in the Latin word splendere, which means bright. Splendid, splendiferous, and resplendent are all related adjectives used to describe grand, magnificent, and brilliant things. Splendor usually has the connotation of luxury or quality, as in "the splendor of Balmoral castle," or "the splendor of the view at the Grand Canyon."