Bathroom Extract Fan

Not sure if this is plumbing or electrical.

I'm plagued with condensation in a bathroom in an old tenement building. I plan to fit a ceiling mounted extractor and duct it to an exterior wall. It's main use will when shower is on. Is there a preferred position for the fan. Bathroom measures about 4m long by about 2.5m wide. Shower id by the door with a window at far end.

Do i mount fan near the window, central or nearer the shower.