Complex sentence: The Hastings Line is built over the difficult, forested, and hilly terrain across the High Weald and sandstone Hastings Beds, necessitating the construction of eight tunnels between Tonbridge and the south coast seaside resort of Hastings.
Split into simpler sentences: The Hastings Line is built over the difficult, forested and hilly, terrain across the High Weald and sandstone Hastings Beds. Necessitating, the construction of eight tunnels between Tonbridge and the south coast seaside resort of Hastings.