This underground ossuary has tunnels and crypts that are both eerie and interesting. The tour takes about 45mins-1 hr. Ages under 14 not allowed w/o companion. €8 adults, €4 ages 14-26, €6 ages 60 up.
This Gothic chapel is possible more beautiful, and definitely more underrated than Notre Dame. The walls are almost entirely made of stained glass, so be sure to go on a sunny day.
They have several paintings from Monet's waterlilies series displayed downstairs. It's also interesting how his paintings changed as he got older, blinder, and crazier.
Go to the roof at night and watch the light show at the eiffel tower, if you're into that sort of thing.
