Monument
noun
Some tombstones are used to write down the thoughts of dead people. They're monuments. They can be really big or really small, but they have to be dedicated to somebody (usually a dead somebody).
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
これは何の記念碑ですか。
What kind of monument is this?