Building in front of you is called De Waag. It's the oldest non-religious building in Amsterdam. It was a part of the city's defensive walls during the Middle Ages and used as a city gate back then. Later on, in 1618, when the city grew it started to be used as a weight house. Don't forget that this neighbourhood was Amsterdam's port. There was a fish market organised at the square in front of it, so they weight the fish in De Waag building. Later on, many city guilds or trade societies had their offices in it. Today, there is a nice restaurant inside.