Tucked away behind the splendour of the Spanish Steps is one of the capital's most poignant shrines â¿“ the apartment where John Keats died

In the spring time, Rome's flower-filled Spanish Steps resemble an out-flung magic carpet. In a riot of colour, they ripple down the steep descent from the twin bell-towered church of Trinità dei Monti, spilling out into the bustling Piazza di Spagna below. Perch on the shallow rim of the piazza's curious Barcaccia fountain (the name means "old boat") and look to the right of the steps at street level, and you'll see a large pink house. Tucked behind the house is a little iron balcony, covered in greenery and crowded with plant pots. And out on the balcony, Catherine Payling, the young curator of the Keats-Shelley Memorial House, is growing violets from seed to take to the grave of the poet John Keats. This is the house where he died on 23 February, 1821, aged 25.

Keats had arrived in the Italian capital in November 1820, shortly after the publication of the volume that contained "Ode on a Grecian Urn", "To Autumn", and "Ode to a Nightingale", now recognised and celebrated as amongst the finest poems in the English language. He was accompanied by the artist Joseph Severn who was to tend his friend devotedly until his death. Keats was suffering from tuberculosis, the condition that had killed his younger brother Tom two years previously, and his doctor had ordered him to abandon north London for a warmer climate that might benefit his failing health.

The poet had arranged to lodge by the Spanish Steps primarily because the doctor who would be treating him lived in the neighbourhood. In fact, the cosmopolitan atmosphere and beauty of Rome's most famous piazza meant that the area had already become a magnet for foreign artists, musicians and poets (Byron had lodged briefly at 66 Piazza di Spagna a few years before Keats's arrival).

Sadly, however, Keats was not to be well enough to join in the expatriate community's convivial breakfasts at the Caffè Greco on nearby Via Condotti, a grand old institution which opened in 1760 and still flourishes. Nor did he write a single line of poetry during his stay.

He wrote only one letter – the heart-breaking farewell to his friend Charles Brown, written on 30 November, which ends: "I can scarcely bid you goodbye even in a letter. I always made an awkward bow." The house where they stayed – 26 Piazza di Spagna – was constructed in 1725 at the same time as the Spanish Steps themselves. In Keats's day it would have been painted a pale yellow or cream, but otherwise, the building remains substantially the same. In 1821, it was run as a boarding house by its (by all accounts, rather fearsome) landlady, Anna Angeletti, and it continued to operate as a pensione until 1906 when it was purchased by the recently-formed Keats-Shelley Memorial Association, an Anglo-American foundation. From 1909, the floor where Keats and Severn lodged has been open to the public as a library and museum celebrating not only the lives of Keats and Shelley (who also died, a year later, in Italy) but the Romantic literature movement in general.

The library has 8,000 books. Catherine Payling recalls causing quite a stir on the Spanish Steps as she and her assistant sat on the balcony carefully brushing the dust from every single one of them, when she took over the curatorship in 1997. The museum, beautifully restored to period style, houses a fascinating collection of manuscripts, autograph letters, paintings and curios.

Some of the exhibits are awesome. No one, surely, could be unmoved on viewing Keats's death mask. But other mementos of literary superstars are as jauntily eclectic as modern-day rock memorabilia. Part of the lock of Milton's hair that inspired a poem by Keats is nested, along with a lock of Elizabeth Barrett Browning's hair, in a silver scallop shell that once belonged to Pope Pius V. Byron is represented by, among other things, a remnant of silk curtain from his bedroom and the wax mask that he wore to a carnival at Ravenna. And mementos of Shelley include a piece of stone taken from the ruined doorway of his former home in Pisa (which was destroyed by bombs during the last war).

But the compelling attraction, inevitably, is the two rooms taken by Severn and Keats, the larger of which served also as their sitting room. Here, Severn played Haydn symphonies on a hired pianoforte in an attempt to lift his friend's spirits. The receipt

for the hire is displayed in a showcase. Here, in the all-too-brief period before Keats was too ill to leave his room, they would discuss their daily passeggiata up the Spanish Steps to Trinatà dei Monti and along the beautiful avenued walkways of the Pincio Gardens, below the Villa Borghese.

They were joined frequently on these promenades by Pauline Borghese, Napoleon's sister, who had taken a shine – to Keats's irritation – to their walking companion, a Lieutenant Elton. In 1805 she had caused a scandal by posing nude for a statue by Canova, which she placed on public display at the Villa, where it still remains. Keats pronounced it "beautiful bad taste".

The room where Keats died is tiny. Nothing is left of the original furniture, which was burned in the piazza after his death to comply with health regulations. The only vestige of their routine of daily living is the fireplace, where Severn either cooked for them both in the evenings or – more usually – heated up food that he'd ordered in from the local trattoria on Via Condotti – Della Lepri ("at the Hare"), now the Bulgari jeweller's shop. But the ceiling, walls and windows of what was to become the poet's living coffin retain a simple tragic dignity.

The lovely painted ceiling with carved flowers, that he must have stared up at from his sick-bed, has been restored to its blue-and-gold original. And two windows, one to the side and one to the front of the room, let in much the same sounds from the world outside as would have been heard nearly 200 years ago. The waters of the fountain still quietly play; horses still pace and snort; throngs of people still bustle and chatter; and – poignantly for the author of "Ode to a Nightingale" – the early morning and evening air still rings with the peal of birdsong.

Keats is buried in the city's Protestant Cemetery, across in Testaccio – now colonised by cats, but nevertheless a tranquil haven carpeted with wild flowers. At his own request, his headstone reads: "Here lies One Whose Name was writ in Water". Back at the house, Catherine shows me one of the museum's most treasured letters, written by Severn to a friend. It tells how, on the day before his death, Keats had sent Severn to see where he would be buried.

To Severn's relief, he was able to report back positively. "Violets were his favourite flower," he wrote ruefully, "and he joyed to hear how they overspread the graves. He assured me that he already seemed to feel the flowers growing over him." I resolve to bring some violets when I return.