What It Means:
"if you seek his monument, look around"
Where It Comes From:
It took 35 years to complete London's magnificent St. Paul's Cathedral. When its architect, Sir Christopher Wren, died twelve years later in 1723, he was entombed inside, under a simple slab of black marble.
Wren's son placed a dedication nearby, which contains the words "Lector, si monumentum requiris, circumspice" ("Reader, if you seek a monument, look around you").
The phrase is generally used to describe a person's legacy and can be taken to mean that what we leave behind (including intangible things like relationships) best represents our life.