Yes, it’s true, it’s very flat. Very good for cycling! The highest natural point is 561’
Fredensborg in North Zealand is really lovely (but again, I’m biased, it’s where my grandparents lived and was my mum’s family home and I love the place, love going ‘home’). You could stay somewhere nearby (Helsingør, for example, then you could take the ferry over to Helsingborg in Sweden, too), and explore the region!