Drew B.
Yelp
There are several must-sees in Ottawa (and it's across-the-river neighbor, Gatineau, QC). I don't know if there's one bigger in that category then Parliament Hill (known simply to most as "The Hill.)"
So, Drew, why the heck are you giving one of the grandest places in all of Canada FOUR stars ... it's friggin' awesome, eh? Agreed, but I found the area very un-visitor-friendly. Where the hell do I enter? Where the hell do I go? We lost about 15 minutes trying to get to the quadrangle (the grassy area in front of Parliament, essentially the main destination). On top of that, we were hamstrung by construction that made things even more confusing.
Once we got there, though, what a place! Keep in mind here that I'm reviewing "The Hill" ... the outdoor area around Parliament, NOT Parliament itself or its interior, which are also awesome. If I were, I'd be giving you recommendations to reserve tickets in advance for the tour ... and also go when the House of Commons and Senate are in session!
For The Hill itself, what a site to see! Built on a rocky, limestone outcrop over 60+ years in the 1800s and early 1900s, it gives visitors a great view of Rideau Canal and the Ottawa River.
More importantly, it gives you an amazing view of what are mostly Neo-Gothic structures that make up the home of Canada's government.
Most prominent in your view is the Peace Tower (Tour de la Paix) and the Centre Block, which Canadians will recognize on their $20 bills. Turning 100 years old next year (2020), the multi-bell tower (campanile) is more than 300 feet (92 metres) tall. Be sure to get up close and personal to this sandstone building and see the hundreds of gargoyles, grotesques, and friezes they've created on the building.
You'll also want to check out the East Block. While it still houses Senators and their staff, its history -- especially the still intact office of Canada's first Prime Minister -- is a sight to see.
To me, the the most visually stunning is the Library of Parliament (Bibliothèque du Parlement). While the Parliament of Canada Yelp page (https://bit.ly/2YjFCgj) does plenty to describe the stunning and also very useful library on the inside, the outside -- and its 16 flying buttresses and other Victorian High Gothic accouterments -- make it a selfie you'll want to leave yourself out of. Beautiful.
At the centre of the quadrangle (where all of this is best viewed) is the Centennial Flame. It was created and dedicated to the 100th anniversary of Canadian confederation (in 1967). Fun fact: It's NOT eternal, but unless you catch it on a maintenance day or when it's hella cold out, it should be whipping up a ferocious natural gas flame. Also check out the surrounding shields for all 13 provinces and territories (Nunavutians, yours is there too!).
The Hill is a great area. It is the metaphoric crown jewel in a city full of great things to see and do.