1. The Rideau Canal
The Rideau Canal connects the city of Ottawa to the city of Kingston. The canal was opened in 1832 as a precautionary measure against American invasion, but today it is used for pleasure boating in the summer, and ice skating in the winter. It is the oldest canal system in North America; it has been registered as a UNESCO site in 2007, and it’s also National Historic Site of Canada.
A section of the Rideau Canal, that goes from picturesque Carleton University past the Parliament Buildings and the luxurious Fairmont Chateau Laurier hotel, becomes the world’s largest skating rink in the cold winter months. While you are skating, try Beaver Tails, a fried dough pastry, and hot chocolate sold in kiosks along the skateway.
2. Byward Market
Located east of the business district, Byward market is a cornucopia of shops, delicatessen, restaurants, and a market for fresh produce during summer months as well as the city's premier bar district frequented by university students and tourists. The market is Canada's oldest operating farmers' market. A four block area around the market is the most densely concentrated place filled with restaurants, cafes, bars and nightclubs. You will also find boutiques and specialy food stores in abundance. Byward Market is also a place for street entertainers to show case their acts. The market is steps away from Rideau shopping centre, Parliament Hill and a number of embassies. Incidentally, the Byward Market construction was surveyed by the same gentleman who was in charge of the construction of the Rideau Canal, Lt.John By of the Royal Engineers.
3. Notre-Dame Cathedral Basilica
Another National Historic site in Ottawa, Notre-Dame Cathedral Basilica is the younger counterpart of the French Notre Dame Cathedral. It is the oldest and largest surviving church in Ottawa. Located in the Lower Town neighbourhood, it is very close to the previously mentioned attractions. Recognized by its twin spires and Gothic style architecture, the richly decorated interior is beautiful and majestic. Check out the ornate altar, impressive Sanctuary and stained glass windows.
Guided tours, that last from 30 to 45 min, are available for individuals or groups from the middle of May to the middle of October although they require you to book in advance. The fee is $75, and for good times to visit, check out their official website. Alternatively, you can just come for a mass and light a candle for a loved one.
4. Parliament Hill
Three Gothic Revival-style buildings are overlooking the Ottawa River. These are the offices of the members of Parliament, the House of Commons and the Senate. They are open to the public although you need to register and get free tickets in the gray building across the street, as well as pass security checks which can take up to an hour. Guided tours cover the grounds of the Parliament Hill, explain Canadian history and the workings of the political system and take about an hour. After the tour, you can walk the grounds and take pictures, especially from the Peace Tower.
5. The Highlander Pub
Located right across Rideau shopping centre, on the way to Byward Market, The Highlander Pub can be easily incorporated into the itinerary. It's a Scottish pub with the sign outside proudly boasting that this the place "where men wear kilts".
Waiting staff is dressed in kilts, and the walls and couches are covered in tartan. The menu has traditional Scottish dishes and some eclectic fare. Try Haggies, traditional Scottish dish, that comes with a wee bit of scotch on the side.
The pub boasts an impressive list of almost 200 different scotch varieties as well as some nice cider and beer. They also have live music after 9pm.
This list is not exhaustive by far since it fails to mention Museum of Civilization or the National Gallery, and tons of other good places. But it's a good start to enjoy Ottawa if you are there only for a few days.