Complex sentence: Spain occupies most of the Iberian Peninsula, and is the second largest country in Western Europe (behind France) and with an average altitude of 650 m, the second highest country in Europe (behind Switzerland).
Split into simpler sentences: Spain occupies most of the Iberian Peninsula, and is the second largest country in Western Europe (behind France). With an average altitude of 650 m, it is the second highest country in Europe (behind Switzerland).