A select few were the first witnesses to another transformation at Mount Aventine, the formerly run-down mansion in Indian Head that has undergone repairs in the past few years.

Oct. 7 marked the opening of a museum in what was once the mansion’s garage, “about an hour before” project volunteers and donors arrived for a celebratory luncheon, said Linda Dyson, vice president of the Friends of Chapman State Park.

The former garage features a display of American Indian and Colonial artifacts collected in the area, mainly from the Mattawoman and Pomonkey creeks, and donated by members of the Friends organization, which works to preserve and promote the park and the mansion it contains, Dyson said.

A sheaf of old tobacco is preserved behind glass, and a stuffed turkey glares from its perch on a giant log in the corner. One wall is devoted to interpreting the history of the Chapman family, which owned the land for more than a century, and the history of the mansion’s last inhabitant, Hungarian Countess Margit Bessenyey, who died in 1984.

Two handmade mourning dresses, worn by Bessenyey after her husband’s death, made their way home and into the display more than two decades after they were sold. Another black dress, a Madison Avenue creation, hangs in an upstairs bedroom. All the garments were donated by Diane Miceli of Fort Washington, who bought them at an estate sale in the mansion’s front yard in the late 1980s.

“I’m a hoarder of nice things,” said Miceli, who admired the dresses’ stylishness but never wore them. She learned about the exhibit from a neighbor of the mansion, a fellow Lion’s Club member, and mentioned she had the countess’ dresses in her closet.

The neighbor asked for them a few weeks ago, and she instantly agreed to give them back, Miceli said. She was “not at all” sorry to part with them because “I’m glad they found a good home, almost like I was saving them for here,” she said.

The exhibit was designed by Joe Namyst of Quality Printers in White Plains, who was hired in July to transform the garage into an interesting and informative space. The first phase focused on the history of the house, but he is designing an exhibit for another wall, now covered in a large forest photograph, that discusses the ecological significance of the land.

“I think what we’re trying to do is get people interested in the facility, in looking at this as historically significant as well as environmentally significant,” he said.

Friends board member Jewell Bragunier was ecstatic about the remodeling of the home’s interior, where sanding, replastering and repainting converted a “terrible mess” into rooms suitable for visitors, she said.

The property has a problem with its septic system, but ultimately Dyson hopes the home could be rented out for events to raise money for upkeep, she said.

The visitor center “really gives us something to build on for what we want to do, which is to be a gateway visitor center, at least for our part of the county,” Dyson said.

Dyson wasn’t sure what the exhibit cost, but said the money came from the Maryland Heritage Areas Authority and a donation by Maryland Del. Peter F. Murphy (D-Charles).

The Friends are now working on a master plan to make the house and grounds more attractive to visitors, said Dyson and Nita Settina, superintendent of the Maryland Park Service.

“I’m just thrilled to see how much progress they’ve made. … We’re not done yet. We have more to do,” Settina said.