Well, Castlevania is a ridiculously anachronistic series, so it's not farfetched. Plus, what with now time travel and all, lots of things are out of place:
-LoS's Mechanical Tower (and Mechanical Monstrosity within)
-LoI's Anti-Soul Mysteries Lab and one grandfather clock room (despite IGA trying to make it an excuse to not have a clocktower stage, this snuck in, despite 'there were no clocks at the time').
-Legends' and CV3's ClockTowers (I believe).
-CoD's Chair Collecting (one of them was a modern office chair!).
-Belmonts' Revenge's 'cloud castle' is floating in the air (though this could be 'magic', not technology).
-Frankenstein's creature existing even before Electricity was invented, from CV3's time all the way to Simon's time... I believe he wouldn't exist until Richter's time.
-Symphony of the Night had a working pseudo-modern elevator system in 1794.
-The Tower of Science and the Castle Center in CV64/LoD intentionally featured models of objects that would not exist until many years later. Although the game takes place in the late 1800's, there are dirigible blimps, transistor radios, Crystal LASER technology, and motorcycles, prior to their time (the tesla coils might be accurate, though).
At this point, at least it can be handwaved by 'Dracula's Magic' or 'St.Germaine/Aeon's influence in the past", etc.