The Matsu (馬祖; Mǎzǔ) group of islands is an overnight boat ride from Taiwan, yet visible from the coast of mainland China. Like similarly located Kinmen, it spent most of the last 70 years as a military outpost. Many of the sights here are defensive tunnels and forts with superb ocean views. A few of these 'strongholds' are being converted into hostels and cafes. Meanwhile a scattering of older traditional houses have survived and a couple of pretty coastal villages present scenes more reminiscent of the Adriatic or southern France.
Note that the term 'Matsu' can refer to the whole archipelago, but is also used in some cases to mean specifically Nangan, the busiest island. And, for good measure, Matsu has temples to Matsu, goddess of the sea, with the world's biggest Matsu statue in Matsu Village, as Magang (馬港) is alternatively known. It's not that confusing really.