The Grand Opera House is referenced as built in 1874 on Sparks St, but also list on Albert Street at O'Connor, built by William Hodgson. http://www.dictionaryofarchitectsincanada.org/architects/view/262 

The next Governor General, the Marquess of Lorne, and his wife, Princess Louise, were greeted in 1879 at the Grand Opera House (Ottawa) (built 1874 on Sparks Street) by Canada's Welcome, a masque with music by Arthur A. Clappé. http://www.thecanadianencyclopedia.ca/en/article/ottawa-ont-emc/ 

February 17, 1885 

Hello Scott, 

Thank you for your question – how fascinating to learn that Mark Twain came to Ottawa! The Grand Opera House was at 134 Albert St., between Metcalfe and O'Connor St. (A Theatre Near You, by Alain Miguelez, 2004, p.30). The building was unfortunately destroyed by fire in 1913. I'm attaching 3 items from the Ottawa Citizen newspaper: an ad for the show from February 16, 1885; an article promoting it from February 17, and a review from February 18. (The review is broken into two files).

I didn’t have much luck finding images of the theatre. Attached is a page from A Theatre Near You with a photo of the interior; and a photo of the exterior in 1897 from the Ottawa Citizen, March 18, 1939, p.2. The photo from the Citizen is also available online here: Ottawa Citizen March 18 1939.  You might also want to contact the City of Ottawa Archives, as they are more likely to have photos of the theatre. Their email is archives@ottawa.ca 

I hope this helps. Please let us know if there is more information that we can provide.

Best Regards,  Romaine Honey  Ottawa Public Library