Shrewsbury's near-island position in a loop of the River Severn created a naturally defensive site that shaped its medieval prosperity. The town centre is a maze of narrow streets and passageways known as "shuts," lined with over 600 listed buildings including magnificent timber-framed structures. Shrewsbury Abbey features in the Brother Cadfael mysteries, while the town was birthplace to Charles Darwin, commemorated in several museums. The riverside Quarry Park hosts the annual Flower Show, one of the longest-running horticultural events in the world.