Generate a photorealistic image of a combined horizon featuring iconic monuments

Generate a photorealistic image of a combined horizon featuring iconic monuments from Rome, Italy, and the snowy mountains of Switzerland with a Swiss train. The image should include the Colosseum, St. Peter's Basilica, and the Trevi Fountain from Rome, naturally integrated into the Swiss mountainous landscape with snowy peaks and the Glacier Express train. In the foreground, depict a happy couple of travelers walking along a path, with backpacks and appropriate clothing for the cold weather. The couple should be looking towards the horizon, appreciating the view. The image should be vivid and realistic, with a natural balance between the Italian and Swiss elements, and lighting suggesting a sunny but cool afternoon.

Avoid unrealistic blending of elements, artificial colors, overexposed lighting, overly bright or dull colors, unrealistic proportions of monuments and landscapes, and unnatural poses or expressions on the couple.