placing a render in an existing enviroment

When architects design a new building which is going to be built amongst exisiting buildings how do you render a drawing like that? I'm a student and i have a building which would be built in the city centre on the river bank with many other buildings to either side of it. I want to render the building but i also want the exisiting buildings to be present in my render if that makes sense. How do architects do that? Do you have to draw the existing buildings yourself which would take a very long time in the centy centre with buildings everywhere.

In a render how do i position my building amongst other buildings to make it look like it's already been built?