Arc de Triomphe
When visiting Paris, especially if it's your first time, you've got a lot a work to do. There's a laundry list of sights and attractions that must be encountered and experienced first hand, and more than likely the Arc de Triomphe is somewhere on that list, and if it's not it needs to be added ASAP. This monument should not be missed by anyone trying to have the whole Parisian experience or that has any kind of appreciation for history.
The arc was commissioned by Napoleon Bonaparte to both beautify the city as well as follow the ancient Roman tradition of building arcs to commemorate battles, victories, leaders and events. The Arch of Titus is directly what the Arc de Triomphe is based off of. Napoleon's triumphal arc's planning began in 1806 and wasn't completed until 1836, well after his death. Carved on the main interior walls are the names of 558 of Napoleon's generals. On the smaller walls the names of key battles of the Napoleonic wars are carved in stone.
The Tomb of the Unknown Soldier is beneath the center of the arc. This portion of the monument was installed in 1920 and was placed there in remembrance of the unidentified dead from both WWI and WWII. There is also an eternal flame lit at the head of the tomb. It's this very same flame that inspired Jacqueline Kennedy to have an eternal flame lit at John F. Kennedy's grave at Arlington Cemetary after his assassination. The eternal flame is also significant because it's the first eternal flame to be lit in Europe since the Vestal Virgin's flame was extinguished in the later fourth century. If you choose to go inside the arch, you need to climb a set of about 40 stairs to reach a museum of items involved with the arch's history.
The arch's location is dead center of a major roundabout involving 12 major city streets, so to access it you'll need to take a specially built underpass at the Avenue de la Grande Armee. You can easily reach the underpass at the Wagram exit at the Metro (you'll want to take metro lines 1, 2 or 6 to get there). At this time their hours of operation run 10 am to 10:30 pm from October to March, then they change to 10 am to 11 pm April through September. For children 17 and under there is no admittance fee. For ages 18 to 25 admittance is 5 euro, and anyone over 25 must pay 8 euro. Be aware that the admittance desk does lock up 30 minutes before the arch is closed for the evening. One of the best days to pay the arch a visit is on July 14, which is Bastille Day, so you can catch the parade.
In closing, just as a tip, if you do place a visit to the Arc de Triomphe on your "to do" list, remember to not get it mixed up with the smaller and less grand Arc de Triomphe du Carrousel that's west of the Louve. Plus keep in mind that the arch is considerably less crowded than the other standard sites such as the Eiffel Tower, and as an additional bonus, is within walking distance of shops, restaurants and other attractions. So don't miss out.