I believe the best way to explore the city is by bike: especially in small european cities. I rented a bike in Amsterdam from Yellow Bike, close to the central station. I was on the bike by myself on the first day, and the second day went on a countryside bike tour. Both were nice. :) Amsterdam is an ideal city to ride a bike: has nice road condition, and the narrow little houses are like homes in the fairy tales. The bike tour was rather tough: 5 hours. I thought I was dying on the bike.