PLEASANT GROVE CITY, Utah  Across the street from City Hall here sits a small park with about a dozen donated buildings and objects  a wishing well, a millstone from the city’s first flour mill and an imposing red granite monument inscribed with the Ten Commandments.

Thirty miles to the north, in Salt Lake City, adherents of a religion called Summum gather in a wood and metal pyramid hard by Interstate 15 to meditate on their Seven Aphorisms, fortified by an alcoholic sacramental nectar they produce and surrounded by mummified animals.

In 2003, the president of the Summum church wrote to the mayor here with a proposal: the church wanted to erect a monument inscribed with the Seven Aphorisms in the city park, “similar in size and nature” to the one devoted to the Ten Commandments.

The city declined, a lawsuit followed and a federal appeals court ruled that the First Amendment required the city to display the Summum monument. The Supreme Court on Wednesday will hear arguments in the case, which could produce the most important free speech decision of the term.