For me Prague is a city that's a combination of ancient and vintage, that never quite gets all the way to modern. Even its metro system feels dated (visually if not functionally). Much of the newer parts of the city (not the 'New City' area, which is some 600 years young, but the more modern outskirts) are darkened by polution from industry during the reign of communism, and have not been cleaned and restored giving it feel of a more industrial age then it really occupies.
You can literally walk from the 1960's back through time until you reach the medieval town area.
The old city if full of nooks and crannies and old narrow streets. Buildings to close together for anything but a person of foot to get through, so separate from more modern constructions that you might as well be back in time.With and Old Town Square which boasts the thing that makes Prague the most steampunk place I can think of...
A huge complicated Astonomical Clock, with figures that animate on the hour, including DEATH. Its a beautiful wonderful contraption, the oldest part, the mechanical clock and astronomical dial, date back to 1410. Later, the calendar dial was added and clock facade decorated with gothic sculptures.
In the 17th century moving statues were added, and figures of the Apostles were added after major repair in 1865-1866.
More information on its history and design can be found in its Wikipedia Entry.
It also has the Black Theatre IMAGE - featuring all sorts of performances a bit like a circus and avant guard caberet in black light. If that's not your idea of steampunk, its still definitely too cool not to mention!
So for me, Prague is my very favorite steampunk city. Bethlehem, PA may be a second favorite, but we'll leave abandoned ore processing plants for another inpirational entry.
Photos © Katherine Dungan and Sarah Dungan (sometimes both at the same time, generally with me flailing and pointing. I like to call it 'art directing'. She likes to call it incredibly annoying and shove the camera at me saying 'you take it'.)