Kropa's main sight is the Iron Forging Museum, which traces the history of iron mining and forging in Kropa and nearby Kamna Gorica from the 14th to the early 20th centuries, though be forewarned: there's little information in English. Nail and spike manufacturing was the town's main industry for most of that period; from giant ones that held the pylons below Venice together to little studs for snow boots, Kropa produced more than 100 varieties in huge quantities.
The museum also has working models of forges, a couple of rooms showing how workers and their families lived in very cramped quarters (up to 45 people in one house) and a special exhibit devoted to the work of Jože Bertoncelj (1901–76), who turned out exquisite wrought-iron gratings, candlesticks, chandeliers and even masks.