noun
BAD : It is impossible to visit all the monuments of London in one day.
GOOD : It is impossible to see all the sights of London in one day.
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monument = (1) a structure, usually made of stone, that is built to remind people of an important event or famous person; memorial: 'The inscription at the foot of the monument read: To all those who gave their lives so that others could live in freedom.
(2) a building or structure that is preserved because of its historical importance: 'If you are interested in ancient monuments you will find the Pyramids fascinating.'
see the sights = visit the interesting places in a city or country: 'I wanted to look round Moscow and see the sights.'