From Alkmaar you can have a good bike trip through the famous land reclamations of the Schermer and the Beemster. Go from Alkmaar to Schermerhorn, where you have a mid-17th-century windmill trio and two more just a few hundred metres to the north. Go south to De Rijp via Grootschermer. Go east to Purmerend via Middenbeemster or follow the traffic-free dyke road, via the fortress Spijkerboor, which also brings you to Purmerend,where you can pick up the train back to Amsterdam.
Other good bike trips are south of Amsterdam. Take the train to Abcoude and follow the meandering small river Gein to Weesp. From Weesp you can follow the river Vecht to Muiden, and from there along a mid-17th-century canal to Naarden, famous for its 17th-century defence works. The station Naarden-Bussum brings you back to the big city.