folly
//ˈfɒli//
Noun
follySingular
folliesPlural
1
Lack of good sense or judgment; foolishness.
It would be folly to ignore the doctor's advice.
2
A foolish act, idea, or practice.
It would be folly to ignore the warning signs.
3
A costly ornamental building with no practical purpose, especially a tower or mock-Gothic ruin built in a large garden or park.
The estate features a Gothic folly overlooking the lake.