There's so much silver and gold that at first it's hard to make out what I'm meant to be looking at. I'm inside the Basilica of the Pillar in Zaragoza and my guide is trying to point out the marble column that the Virgin Mary is said to have brought here for St James in AD40.
Finally I spot it, a small column a few feet high encased in silver and topped by a little statue of the Virgin. This pillar, which has stood in a church on this site since at least the ninth century, is now an object of pilgrimage for Catholics worldwide.
I don't believe in miracles, but this modest piece of marble seems to have brought luck to Zaragoza. This ancient settlement, 190 miles north-west of Barcelona, has survived sieges to become one of the richest and most beautiful cities in Spain.
It helps that Zaragoza sits in a fertile and strategic site along the river Ebro. The Romans founded the city in 14BC and it grew to become one of the most important urban centres in Hispania. The Roman street plan still defines the city's heart and you can visit the remains of the forum, baths and theatre.
From 714 to 1118 Zaragoza was part of an Islamic kingdom, the legacy of which includes an impressive palace – the Aljaferia – and the highly patterned Mudejar brickwork, which you can see in its finest form on the walls of the city's cathedral, St Salvador (known as La Seo).
Not surprisingly, these monumental buildings featured prominently in my plans. But I was also keen to try its famous food and wine. Aragon, of which it is the regional capital, has some of the best vineyards in Spain, and the city's celebrated tapas come in a mind-boggling variety. I was also excited about getting a sneak preview of Expo 2008, a three-month festival on the theme of water and sustainable development, which starts this Saturday on the banks of the Ebro.
There is an easy walking route between the cathedral square and El Tubo, an area of tightly packed narrow streets where you can find all the best places to eat and drink. Bodegas Almau, at Estebanes 10, is a good place to try a prized wine from Aragon's Carinena region and the bar's specialities of cured anchovy or goat's cheese. One of the most atmospheric places I found was Bodeguilla de la Santa Cruz, at Santa Cruz 3, with its series of cosy little rooms.
The next day I took the 20-minute walk along the river to visit the Expo site. Here, 62 acres of riverbank accommodate displays on the theme of water from more than 100 countries. Most of the exhibits will be housed in a central building which snakes through the site. But it's the landmark-themed pavilions that stand out, the most startling is the bridge across the Ebro designed by the London-based architect Zaha Hadid.
Everything at the Expo has the highest green credentials: the buildings are energy efficient; water will be recycled; carrier bags are made of potato starch and the passenger boats will be solar powered. There will be lots of fun, too. There is a huge aquarium displaying life from five great rivers, while 3,400 shows are planned, including a nightly spectacle along the riverbank. Performers include Bob Dylan, who recorded the official Expo song.
But given the heat of the Spanish summer, perhaps the most popular part of the Expo will be the new water park. Here the waters have been diverted to create beaches and a stretch for white-water rafting.
After lunch I headed off to see the work of the city's most famous son, Francisco de Goya. You can see his early frescos in the cupolas of the Basilica and a complete set of his etchings in the Camon Aznar Museum. A project to build a Goya museum is under way.
During a second visit to the Basilica, I noticed two bombs hanging on the wall. They fell through the roof during the Spanish Civil War but failed to explode. The clean holes, one right through a Goya fresco, have been preserved as evidence of the miracle. Some people say the pilot defused the bombs in a fit of guilt, but I prefer to see it as just another example of this charming city's long and happy run of luck.
How to get there
Return flights to Zaragoza with Ryanair (0871 246 0000; www.ryanair.com) cost from £93. Marcus Field stayed at the NH Gran Hotel Zaragoza (00 34 976 221 901; www.nh-hotels.com), where doubles cost €222 per night.
For Simon Calder's prescription on how best to spend 48 Hours in Zaragoza, click here