Doom

Before Doom there were partial implementations including Castle Wolfenstein [survey]

Choosing a 3D game engine to attempt will take research.  Dublin's streets are not all at right angles, and the sky is almost always visible.

Wireframe 3D might be more effective for the first try. Buildings would need basic dimensions in addition to streets and sidewalks.[typology of buildings] The census form 'House and Building Return (Form B1)' includes a count of windows in front.

there must have been open spaces: parks, rivers, vacant lots? calculating the view

boiling it down to a handful of standard blocks

interactive Flash demo