Citadellet is the best-preserved Renaissance fortress in Sweden and the undeniable centrepiece of Landskrona. The 16th-century castle sits at the heart of the town, surrounded by a wide moat and some of the finest earthwork fortifications in northern Europe — massive grassy ramparts that have survived largely intact because nobody tried to demolish them.
The castle itself houses a museum covering the history of the fortress and the town, with a particular focus on the period when this stretch of coast was a contested frontier between Sweden and Denmark. The views from the ramparts over the Öresund are excellent, and the surrounding park makes a pleasant afternoon walk even without going inside.
The complex is open for guided tours in summer; parts are accessible year-round. Check the Landskrona Museum website for current hours and admission prices.