Travel brochures can boast about breathtaking Zion, Bryce and Arches national parks. Tourism promoters can roar about Dinosaur National Monument and hawk the state's high peaks.

But Utah's hottest tourism destination is Temple Square and the campus around it, which, as the headquarters of The Church of Jesus Christ of Latter-day Saints, is the heart of the Mormon church. Covering three city blocks, the church's grounds in downtown Salt Lake City draw 3 million to 5 million visitors a year, the church and the state Office of Tourism said.

By comparison, Utah's five national parks drew 5.3 million visitors in 2005, the tourism office said.

And it's not just Mormons who tour the square's 15 attractions on the church's pioneer history, art, faith and genealogy.

"We're curious about their religion and their history," said Darlene Davis of Walker, La., who was also here on business. "But it's just curiosity. We're not interested in being converted or anything."

The Mormon faith is one of the world's fastest-growing religions, with an estimated 12 million members worldwide. As its influence grows, so, too, does interest in Joseph Smith, who said he was directed to found the church by spiritual visions beginning in 1820, said Kim Farah, a church spokeswoman.

Even a quick, 30-minute tour of the grounds reveals a history of epic American drama and Western adventure: Smith's death at the hands of an angry mob; early Mormons fleeing religious persecution in the Midwest; controversy over a church doctrine (officially abandoned in 1890) that endorsed polygamy; and Mormon pioneers who trekked across the plains to find refuge and build a city near the shores of the Great Salt Lake.

Like visitors to St. Peter's Square in Rome, people touring Temple Square should expect to find a church-sanctioned version of history. Don't come looking for a lengthy discussion of polygamy or a detailed explanation of the "Utah War" of 1857, when Mormon militia and federal troops engaged in a tense standoff.

You will, however, encounter some of the most polite, articulate hosts imaginable. And if Utah is known for its trademark "Greatest snow on Earth," the church's grounds could qualify for "the cleanest show on Earth." From the ornate gardens to the two visitor centers, three restaurants and even the restrooms, the campus is a testimony to a Mormon sense of meticulous cleanliness and order.

About 150 young women missionaries, speaking more than 30 languages, lead the tours. Visitors will stop outside the grand Salt Lake Temple (non-Mormons are not allowed inside because it is considered sacred ground) and the Tabernacle (traditional home to the Mormon Tabernacle Choir, it is closed until 2007 for renovations). But they can enter the 1882 Assembly Hall, the 1854 Beehive House of Brigham Young, art galleries and visitors centers.