One of the most intriguing museums in America is located down a narrow road, behind a stone wall, hidden by hills. Called Glenstone, it’s in Montgomery County, Maryland, just beyond the Washington, D.C., subdivisions named after bygone farms. According to the art collector Alain Servais, it is “probably the best private museum and collection on earth.” You can visit for free.

Founded by the philanthropist Mitchell P. Rales (net worth: $6 billion) and his wife, Emily Wei Rales, who is the museum’s director, Glenstone opened in 2006, underwent a major expansion in 2018, closed during the pandemic, and then closed again in 2024 for a roof repair in the new exhibition hall. The museum is now fully open again.