Answer: boulder

AnswerCrossword Clue
BOULDERMile-high city
BOULDERDenver neighbor
BOULDERCity near Denver.
BOULDERLarge mass of rock.
BOULDERCity just E of Front Range.
BOULDERHoover Dam's old name
BOULDERPlymouth Rock, e.g.
BOULDERCity near the world's highest dam
BOULDERObstruction at the entrance to a cave, maybe
BOULDERRock that may be hard to roll
BOULDERColorado college town
BOULDERColorado River dam (officially "Hoover")
BOULDERHeavy rock
boulderA large rock, typically one that has been worn smooth by erosion
bouldera large rock, also BOWLDER