Formal:
* The museum's collection of ancient artifacts was marvelous.
* The scientist's groundbreaking research yielded marvelous results.
* Her performance on stage was marvelous, leaving the audience in awe.
Informal:
* That cake is marvelous! I want another slice.
* We had a marvelous time at the amusement park.
* The view from the mountaintop was simply marvelous.
Descriptive:
* The sunset painted the sky with marvelous hues of orange and purple.
* The intricate details of the tapestry were marvelous to behold.
* He had a marvelous sense of humor that always kept everyone entertained.
Remember, "marvelous" is an adjective that means "extraordinary," "wonderful," or "amazing." Choose the sentence that best fits the context you want to convey.