The obelisk marks the Place de la Concorde, formerly the Place de la Revolution where Louis XVI, Marie Antoinette, and Robespierre were guillotined. The gold dome is the Dome Church, which houses Napoleon's sarcophagus.
The Louvre.
In the late 18th century Paris's cemeteries overflowed and became unsanitary. So, their remains were moved to former mines under the city, which are now a creepy tourist attraction. There are remains of 6 millions people there.
