Vor Frelsers Kirke Copenhagen

It's hard to miss this 17th-century church and its 95m-high spiral tower. For a soul-stirring city view, make the head-spinning 400-step ascent to the top – the last 150 steps run along the outside rim of the tower, narrowing to the point where they literally disappear at the top. Inspired by Borromini's tower of St Ivo in Rome, the spire was added in 1752 by Lauritz de Thurah. Inside the church, highlights include an ornate baroque altar and elaborately carved pipe organ from 1698.