Located just outside of Barcelona and sited on steel hill overlooking a valley and the Mediterranean sea, X-House by Spanish architectural studio Cadaval & Sola-Morales has bold, fully-glazed angled frontages that look out to stunning views of the surrounding landscape. Available through ownersdirect.co.uk  Photo 4 of 10 in 10 Cliffside Destinations That Will Make You Feel on Top of the World