What are the furthest points North, South, East and West you have visited?
These four points can be used to define a rectangle (well, in more-or-less spherical geometry they do) whose borders lie along the lines of latitude and longitude you have identified. What's at the centre of this region? Have you been there? Where is the nearest place to the centre you have visited?
North - Aultbea, Scotland: 57.833°N
East - Budapest, Hungary: 19.083°E
South - Mahon, Menorca: 39.883°N
West - Aultbea, Scotland: (-)5.583°W
which makes for a midpoint of 48.858°N 6.75°E, some miles west of Strasbourg. The nearest I have been to there is Frankfurt am Main.