First of all, Renaissance Man achievement can be obtained while playing Showcase Art of War, which is part of the newly released Art of War charity DLC.

Once you are safely inside the Lars Blanken Gallery, find a lonely man with a backpack looking at some fine art in the first room of the gallery. There are several people with backpacks in the whole gallery, but as far as I know, this one is the only one with a binoculars in his pack.

Simply approach him, open the inventory and take the binoculars. Don't worry, he will be okay without it, he shouldn't even complain, because you are not on Altis anymore, you are in Amsterdam. And all the people here are apparently very nice and don't know the concept of "theft". So don't believe the description of the achievement, you actually stole nothing.

Anyway. With the binoculars happily provided by that kind man with a backpack, head to the central room of the gallery, use the binoculars and look through a specific window seen in the screenshot below:


Now all you have to do is focus on the left tower of a cathedral seen through this window. There you should see one very specific man with his own binoculars, surely stolen from a backpack of some poor unsuspecting soul (which is something you absolutely did not do, remember).

You may have to zoom in a little, but once you'll safely spot the man, the achievement should be yours. Now you can speculate what he's doing up there.