ball (formal dance event)

an area with sides higher than the center: an indentation, a depression, a dip, a divot, a hole / (slang) female genitalia, the vagina

a sunken center / a place or object with a sunken center

an indentation, a dip or divot, a hollow, a dent in a surface

grave; graveyard

bureau / board / office

thumb

think

hollow / pit / depression / swamp

curving shoreline, bend in a river