Stone bridge

https://www.cgtrader.com/3d-models/architectural-details/construction-engineering/stone-bridge--4

https://ua.3dexport.com/3dmodel-stone-bridge-166422.htm

http://www.turbosquid.com/FullPreview/Index.cfm?ID=896564&seo=0

River valley low poly asset

https://www.cgtrader.com/3d-models/architectural-exterior/landscape/river-valley-bridge-low-poly-asset

https://ua.3dexport.com/3dmodel-river-valley-low-poly-asset-166409.htm

http://www.turbosquid.com/FullPreview/Index.cfm?ID=896830&seo=0