The most obvious day trip from Helsingborg requires no planning at all: walk onto a ferry and twenty minutes later you are in Helsingør in Denmark. Kronborg Castle — Elsinore, the setting of Shakespeare's Hamlet — is right next to the ferry terminal on the Danish side. The old town of Helsingør is well-preserved and worth an afternoon. Return ferries run every few minutes until late in the evening.
The Kullaberg peninsula, about 30 kilometres to the northwest, is worth a longer excursion. The nature reserve at its tip has dramatic sea cliffs, a lighthouse, and walking trails through heather moorland. Mölle, the small resort village on the peninsula's north shore, has good seafood restaurants.
