Upon its completion in 1863, the mansion of 72 rooms surpassed "in size and cost any dwelling-house in Canada," exceeding Dundurn Castle, built by Sir Allan MacNab in 1835.

Although reduced in size and lacking its former grandeur, Ravenscrag continues to dominate what remains of the Golden Square Mile today.

Victor Roy designed Allan's residence in the style of an Italian Renaissance villa or palazzo, made popular in England since the construction of Osborne House for Queen Victoria and Prince Albert in 1851.

[5] The reception rooms were built of a size and style compatible for society gatherings and to receive royalty, the first instance of which occurred in 1869 when the Allans entertained the young Prince Arthur during his year in Montreal with the Rifle Brigade.

[9] In 1872, the first ball was held at Ravenscrag in honour of the new Governor General of Canada, Lord Dufferin, when the Allans invited 400 guests.

[10] Allan's favourite room was his library on the ground floor, where he whiled away the hours working, relaxing or playing with his children.

The room was typically Victorian and dominated by a wall-to-wall mahogany bookcase, decorated with carved panels depicting sea monsters and mermaids.

As might have been expected for a house of its kind in Montreal, Ravenscrag was fitted with gas lighting and the most advanced plumbing and heating technology available at the time.