I can thoroughly recommend both the Notre Dame and Latin Quarter walks with this company. The guides are knowledgable and share their information in a fun and informative way. I learned more about notre dame than I had thought possible from simply walking around the outside of the building and along surrounding streets. you give what you think the tour was worth. Most goes to the guide and a portion to the company for publicity. At the end of the walk each particpant is given a 'perks' envelope. Some good info and vouchers contained within. Guides are happy to answer more general questions about Paris in addition to discussion on the walk theme. Not having to book was a plus, as you just head to the meeting point and join the group.