Similar words
stattlich
stattlich is more about size or stature, like a stately, sizeable building or person; imposant is more about impressiveness generally.
Similar in other languages
Spanish
imponente
imponente is the Spanish word for the same thing — both mean "imposing."
Practice
1 What does imposant mean?
imposing
2 Fill the gap: Das Schloss ist ___.
Full sentence: Das Schloss ist imposant. (The castle is imposing.)
3 Which fingerprint chart matches imposant?
imposant: neutral register, common frequency, general domain, neutral connotation.