A guided tour of Les Egouts (the sewers) is an unusual and surprisingly enjoyable way to learn some fascinating history of Paris.
English speaking guides have some great anecdotes as they guide you through the underground tunnels.
The smell is not offensive! Tours take place Saturday to Wednesday between 11 a.m and 5p.m. The entrance is near the Eiffel Tower at 93 Quai d'Orsay.