John Belcher designed it. Construction ran from 1907 to 1909. The plan is essentially a domed pavilion in the Edwardian Baroque manner: heavy stone steps in Cornish granite leading up to a great central space topped by a copper-clad dome 150 feet above the ground. The structural trick is modern and invisible - Portland stone hung as a weatherproof skin on a steel frame, the same engineering principle that built skyscrapers. That steelwork has caused most of the conservation headaches of the past century, as Edwardian rivets and bolts have rusted within the stone they were meant to support. The building is what the British call a folly, but folly is the wrong word for something this serious. It was built to last.

Around the exterior of the dome, sculptor Herbert Hampton carved four allegorical figures: Commerce, Science, Industry, and Art. Hampton had completed the Queen Victoria Memorial in Lancaster's Dalton Square the previous year, also commissioned by Lord Ashton, so the family style is consistent. Inside the dome are painted allegories of Commerce, Art, and History by George Murray, and decorative work whose plaster mouldings were inspired by Islamic architecture - an unexpected element in an English Edwardian monument. The floor is laid in white, black, and red marble. The whole interior is now used for exhibitions, concerts, and weddings, but the original purpose was simpler: to give Lancaster a building grand enough to hold a single absence.

James Williamson, 1st Baron Ashton, was Lancaster's linoleum king. His Storeys Lune Mills factory dominated the town's economy for decades, producing oilcloth and floor coverings that sold across the British Empire. He was one of the wealthiest commoners in Edwardian England before his peerage in 1895, and he gave Lancaster much: Williamson Park itself, the Queen Victoria Memorial, hospital wings, and after Jessy's death, this enormous dome. He was, by contemporary accounts, a difficult man - litigious, controlling, capable of sudden generosity. The Ashton Memorial is the architectural form of grief filtered through someone who would not accept that grief should be modest. The Taj Mahal comparison is not hyperbole; it was the comparison the architects themselves used.

Williamson Park sits on Lancaster Moor, the high ground east of the city. Climb the granite steps to the colonnade and the view runs west over Lancaster's rooftops to the spires of Lancaster Cathedral and Lancaster Priory, then on to the broad estuary of Morecambe Bay and, beyond it, the hills of the Lake District fading north. On a clear evening the dome turns gold in the sunset. By coincidence, the memorial stands very close to the mathematical centre point of the United Kingdom of Great Britain and Northern Ireland - a fact noted on plaques and discussed in Ordnance Survey circles. It seems fitting that a building this large should also be, almost accidentally, exactly in the middle.