I used to wonder how the Apostles managed to find an audience to hear the Gospel in the first century. The above photo shows what remains of the suggestum on the west side of the Forum. From this public "soap box" anyone could quote a poem or sing a song they had composed or play a musical composition or simply speak about any topic imaginable. Probably the best known modern equivalent is in London's Hyde Park. Called "Speaker's Corner," it is one of Britain's most famous places for impromptu public debate and discussion.
From Acts 17:17, Therefore [Paul] reasoned ... in the marketplace [or forum, called "agora" in Greece] daily with those who happened to be there.