The Pevsner architectural guide to the historic county of Glamorgan judges Cathays Park to be "the finest civic centre in the British Isles".

On 14 December 1898, the local council bought the entire 59 acres (24 ha) of land for £161,000 from the Marquess of Bute[5] (equivalent to £22 million in 2023[6]).

A six-month Cardiff Fine Arts, Industrial and Maritime Exhibition which included specially constructed boating lake, a wooden cycling track and an electric railway was held in 1896.

[8] The second phase was built in a more simplified classical design of the Temple of Peace, Cathays Park 1, Cardiff Technical College, now Bute Building.

[8] The four-storey maximum rule which was imposed by the local authority to ensure that no building in Cathays Park overshadowed the City Hall was removed.

[8] At the start of the first phase in 1897 a competition was held for a complex comprising Law Courts and a Town Hall, with Alfred Waterhouse, architect of the Natural History Museum in London, as judge.

The east and west pavilions of both façades are identical in design, except for the attic storeys, which are decorated with allegorical sculptural groups.

[11] The third plot on the site facing City Hall lawn went empty until 1910, when the competition for a National Museum of Wales was won by the architects Arnold Dunbar Smith and Cecil Brewer.

The Museum site was not bounded to the north by an avenue so there were scarcely any limits on the depth of the building; the 1910 plan was almost twice as deep as it was broad.

[13] Further extensions came only in the 1960s and 1990s; these remained faithful to the original design on the exterior (and included sculpture by Dhruva Mistry) but are of a neutral character on the inside.

Although the architect and town planner, John B. Hilling, in his study Black Gold, White City: The History and Architecture of Cardiff Civic Centre published in 2016, acknowledged the architects' efforts to respect Cathays Park 2's surroundings, by use of a symmetrical plan laid out on a clear axis, the building's Brutalist style has been much criticised.

Both Hilling and the architectural historian John Newman quote the judgement of the Architects' Journal; "a perversely appropriate symbol of closed inaccessible government" [suggesting] a bureaucracy under siege".

"[23] In his Glamorgan volume of the Pevsner Buildings of Wales series, Newman described Cathays Park as "the finest civic centre in the British Isles".

[27] Revisiting the subject in his 2018 revised The Architecture of Wales: from the first to the twenty-first century, Hilling agreed, contending that Cathays validated, "as much as anything, [Cardiff]'s claim to city status and national capital".

The later 20th and 21st centuries have seen the erection of a large number of memorials in the park which have generated some criticism; John Hilling attacked the "ill-considered and uncoordinated way [the monuments are] scattered across the gardens".

The 2 acres (0.81 ha) garden has as its centrepiece a stone circle constructed in 1899,[35] when the National Eisteddfod of Wales was held in Cardiff.

[40][46] One of the strict conditions of the sale of Cathays Park by the 3rd Marquess of Bute was that the trees must be preserved and that no buildings should ever be built on the site of the gardens.

It was designed to be aligned with the main thoroughfare of King Edward VII Avenue, on a site that was originally planned for a Welsh Parliament House.

Parc Mackenzie, which lies between the University of Wales main block and the National Museum, is the newest area of green space to be created within the park.