The National Folk Festival (USA) used to be held at Wolf Trap Farms Park in Virginia, near Wash. D.C....the is a tunnel(sort of ceramic lined) going from one parking lot to the path to the main gate...a group of us were walking through it and talking, and the sound was amazing..so we stopped and the woman who is now the president of FSGW, Carly Gewirz, sang "Cabin in the Corner of Gloryland"...it still raises the hair on the back of my neck to remember it! Not the sort of acoustics you'd want for most concerts, but WOW!!