As well as a stock of memories and images, travel also provided perspective. He spent the summer of 1816 with Byron at Lake Geneva, where he wrote Mont Blanc, with its pantheistic sense of the power and unity of nature. The way Shelley is moved by Mont Blanc to a rumination on the invisible forces at work in nature is typically Romantic. He is not describing the scene, but exploring the emotions it evoked. Don't be misled by the success of WH Auden and Louis MacNeice's jaunty Letters From Iceland.
Poets are thoroughly unreliable travellers.
Robert Browning, widely travelled and much influenced by Shelley, settled in Florence in the 1850s but wrote virtually nothing while there. Jerusalem Athens Alexandria Vienna London Unreal. Some poets are explicitly doubtful about the benefits of travel. The resolutely immobile Philip Larkin once expressed an interest in visiting China, but only if he could come back the same day. Travel broadens the mind, but great poetry is often the product of narrow obsession, the neurotic cultivation of a tiny plot.