(in no particular order, though pit is my favorite so lets start there) {dinnerpit}
pit
hole
depression
dig site
canyon
crater
chasm
quarry
cut
valley
bowl
dip
basin
void
abyss
absence
ditch
gutter
trough
cave
cavern
alcove
cove
grotto
manhole
bioswale
indent
gap
crevasse
crack
fissure
cavity
opening
rift
fissure
split
corner
shaft
tunnel
burrow
drain
entrance
window
notch
carving
recess
dell
culvert
bund
what’s missing?