Map of Ancient Rome

I finally found a way of doing it. I must say, I'm speechless about the versatility of Mathematica. Watching this YouTube video was key: Historical Information in Wolfram|Alpha and the Wolfram Language.

redDot = Graphics[{Red, Disk[]}];
blueDot = Graphics[{Blue, Disk[]}];

Rome = Entity["City", {"Rome", "Lazio", "Italy"}];
LakeTrasimeno = Entity["Lake", "LakeTrasimeno::946n7"];

GeoGraphics[{{Polygon[
    Dated[Entity["HistoricalCountry", "RomanRepublic"], 
     Entity["MilitaryConflict", "SecondPunicWar"]["StartDate"]]]},
  {GeoMarker[Rome, redDot, "Scale" -> Scaled[0.02]], Black, 
   Text[Style["Rome", Bold], Rome, {-1.5, 0}]},
  {GeoMarker[LakeTrasimeno, blueDot, "Scale" -> Scaled[0.02]], Black, 
   Text[Style["Trasimeno", Bold], LakeTrasimeno, {-1.2, 0}]}
  },
 GeoBackground -> {"CountryBorders", 
   Entity["MilitaryConflict", "SecondPunicWar"]["StartDate"]},
 GeoRange -> Quantity[1000, "Kilometers"]]

Note: I used the natural language input feature a lot, but it doesn't show in the code above. For example, I would type ^= and write Second Punic War and get Entity["MilitaryConflict", "SecondPunicWar"]. I wish I knew a way to see what are the attributes of Entities like these. It took me a while to figure out how to extract the start date...

Answer to the original question

Here's the map of the Roman Republic in 250BC.

redDot = Graphics[{Red, Disk[]}];
blueDot = Graphics[{Blue, Disk[]}];

Rome = Entity["City", {"Rome", "Lazio", "Italy"}];
LakeTrasimeno = Entity["Lake", "LakeTrasimeno::946n7"];

GeoGraphics[{{Polygon[
    Dated[Entity["HistoricalCountry", "RomanRepublic"], 
     DateObject[{-250}]]]},
  {GeoMarker[Rome, redDot, "Scale" -> Scaled[0.02]], Black, 
   Text[Style["Rome", Bold], Rome, {-1.5, 0}]},
  {GeoMarker[LakeTrasimeno, blueDot, "Scale" -> Scaled[0.02]], Black, 
   Text[Style["Trasimeno", Bold], LakeTrasimeno, {-1.2, 0}]}
  },
 GeoBackground -> {"CountryBorders", DateObject[{-250}]},
 GeoRange -> Quantity[1000, "Kilometers"]]

redDot = Graphics[{Red, Disk[]}];
blueDot = Graphics[{Blue, Disk[]}];
Rome = Entity["City", {"Rome", "Lazio", "Italy"}];
LakeTrasimeno = Entity["Lake", "LakeTrasimeno::946n7"];
GeoGraphics[{Polygon[
   Entity["HistoricalCountry", "RomanEmpire"]], {GeoMarker[Rome, 
    redDot, "Scale" -> Scaled[0.02]], Black, 
   Text[Style["Rome", Bold], Rome, {-1.5, 0}]}, {GeoMarker[
    LakeTrasimeno, blueDot, "Scale" -> Scaled[0.02]], Black, 
   Text[Style["Trasimeno", Bold], LakeTrasimeno, {-1.2, 0}]}}, 
 GeoBackground -> Dated["CountryBorders", -250], 
 GeoRange -> Quantity[1000, "Kilometers"]]