NAUVOO, Ill. — The "city beautiful" is coming of age — and quickly.

With a modern population equivalent to only 10 percent of the 12,000 people who settled this former swamp in the 19th century, Nauvoo will experience a new influx of people come Monday. That's when the first wave of 350,000 visitors is to arrive for the beginning of a six-week open house for the newly reconstructed Nauvoo Temple, whose presence atop a hill west of the town's business district matches its predecessor's location and grandeur in exacting detail.

The building's first dedication ceremony on June 27 will be a watershed moment for The Church of Jesus Christ of Latter-day Saints. Early members abandoned the first Nauvoo Temple and headed west to the Rocky Mountains in 1846 after years of intense persecution.

A small group stayed in Nauvoo, finishing the temple three months later. An arson fire destroyed the temple's interior in October 1848, and a tornado in May 1850 knocked down one wall and weakened others. The remainder of the temple walls were eventually taken down.

A century and a half later, descendants of those early church members are returning by the hundreds of thousands to a place that for many is as much an LDS heartland as Salt Lake City is a homeland.

One of them is President Gordon B. Hinckley, who set the reconstruction in motion in April 1999 with an announcement that the temple would be rebuilt.

His father, Bryant S. Hinckley, was a mission president in the Midwest area that encompassed Nauvoo in 1939 — the 100th anniversary of the town's beginnings. Bryant S. Hinckley suggested that the temple be rebuilt.

"But there were obstacles; nothing could happen, nothing did happen," President Hinckley told one interviewer. "And now, 60 years later, it's happening, and to me it's a source of great satisfaction. My grandfather was (in Nauvoo) as a young man, my father was there as a mission president and mine has been the opportunity to move forward the reconstruction of that temple."

President Hinckley told builders he wanted the temple's exterior to be as close to the original as possible, with the same hand-carved stonework that made the original an unprecedented achievement on what was then the edge of the wild frontier.

As for the interior, designers and builders stayed as true as possible to the decor, furnishings and feel of the old temple while incorporating such modern features as electric light fixtures, heating, air conditioning, plumbing and earthquake-resistant design.

A copy of the temple's original architectural plans served as the basis for the reconstruction. Detailed plans for the reconstruction emerged after a committee spent weeks researching journals, historical documents and libraries.