In 2004 I went on my first ever trip outside of Canada, a 17-day Contiki tour all over Europe. The countries I visited were England, France, Belgium, The Netherlands, Germany, Austria, Switzerland, Lichtenstein, Italy, Vatican City and Monaco. Taking a Contiki to Europe by myself in my early 20's was a great idea and experience and I would recommend it to anyone who does not have a travelling companion.
Even though I was by myself when I first came to England for the tour, I never had to travel on my own. I had the comfort and camaraderie of travelling in a group. Although I did not have a travelling partner to share my memories with, I made friends along the way with whom I could share those memories.
During the trip I was able to visit many different places for a relatively cheap price. On a Contiki tour you don't have to make your own hotel arrangements and all the bus travel is provided for you. Because of their size, Contiki is able to get great volume discounts for accommodations and tourist attractions that you would never be able to get if you went independently as a backpacker. The hotels are safe and have good facilities so you don't have to put up with hostels as backpackers on a budget do. The only disadvantage compared to backpacking is that there is a somewhat rigid schedule to go on as opposed to backpacking where you can stay in a certain place for as long as you want.
While backpacking can have adventure, I liked the advantage of having a very knowledgeable tour guide provided by Contiki. If there is a specific activity you wish to do or site you want to see while in a certain European city your tour guide can send you off in the right direction quickly and may even be able to pull some strings for you regarding price or quality of service.
Finally, since the focus of a Contiki tour is the 18-35 age demographic, you will meet many young people and be able to go on many social outings during your trip. Often other Contiki tour groups cross paths on more than one occasion so while your group may already be large from anywhere between 30-50 people, you have an opportunity to meet many more tourists as well as young locals on your tour.
If you are interested in other Contiki tours, you can read my article Doing a Greek Island Hopping Tour.