Draw the streets as lines and the blocks between them as areas, add the river, the church, the station and the police, and set each street’s name along the street itself, the way a printed plan does.
Print it as a 1920s town plan for an investigation or as a sketch somebody drew on the spot, A4 or A3 at 300 DPI, and hand it over with a cross already pencilled in. For the country around the town, use the Region map.