When you walk into the vast open space of the Bibi-Khanum Mosque, crowning glory of the storied city of Samarkand, you're well advised not to look up. Unfortunately I failed to follow that advice.
At the top of the doorway through which I entered was a huge crack extending all the way to the window above; the arch at the top of that window had fallen in, leaving a gaping hole; from the hole a network of finer cracks extended all the way up the wall to the base of the giant dome; the whole structure looked as though it might collapse at any minute.
I did stay in there long enough to take some photos, marvel at the scale of the huge building and try to imagine how magnificent it must have seemed when it was completed in 1404. But, frankly, I didn't feel entirely safe with all that flawed masonry overhead and it was quite a relief to escape back to the sunshine.
Until recently, apparently, people weren't allowed inside at all. Ramil, our Tartar guide, gestured at the bits of steel reinforcing poking from the structure and commented, "If it wasn't for the work of the Russian engineers who patched it up in the seventies and eighties this would not be standing."
Yet this cathedral mosque was supposed to have been the greatest monument to the reign of the mighty conqueror remembered here in Uzbekistan as Emir Timur but known in the west as Tamerlane (from his derisive nickname Timur the Lame).
All the resources from Timur's victories in Central Asia and Persia, Russia and India - craftsmen and elephants, gold and jewels - were poured into making Samarkand the most magnificent capital in the world and the Bibi-Khanum Mosque the greatest symbol of Islam.
So determined was he to astound the world that he reportedly returned from one of his wars and, deciding the minaret towers were too low, executed the architects and took over supervision of the project himself, encouraging the workforce by whipping laggards and tossing pieces of meat to hard workers.
It was intended, quite explicitly, as a statement of worldly triumph, as Timur made clear when he declared, "Let he who doubts our power look upon our buildings."
Instead it started to crumble shortly after his death (less than a year after work was finished), finally collapsed in an earthquake in 1897 and today is more of a monument to the transient nature of human achievements than a statement of eternal glory.
It reminded me vividly of Percy Bysshe Shelley's poem Ozymandias which describes a ruined statue in the desert and concludes with the lines:
"And on the pedestal these words appear:
'My name is Ozymandias, king of kings:
Look on my works, ye Mighty, and despair!'
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away."
But, while Timur may not have achieved the everlasting glory he desired, he certainly made Samarkand a spectacular city in his lifetime and it remains a fascinating place to visit today.
Even in its dilapidated state the cathedral mosque is a majestic sight. Its huge prayer hall, topped with a dome 20m in diameter and reaching 40m above the ground, stands at the centre of an enormous enclosed courtyard covering nearly 2ha and designed to hold 15,000 worshippers, girdled round with walls, minarettes, religious buildings and a massive entrance 35m high.
If it's this impressive today, I thought, as I peered through another badly cracked doorway, imagine what it must have been like when it was built. According to Ramil, the restored entrance gate and the minarets are only two-thirds the height of the original structures; the huge interior of the main dome is now bare but once was lined with magnificent mosaics made from precious stones; and before the earthquake there were several more giant domes around the perimeter of the complex.
No wonder visitors to Timur's court - including an envoy from the King of Spain - were stunned at its size and beauty.
Indeed, in many ways the fact that his cathedral mosque is showing its great age, has developed a few of the wrinkles which come with the passing of time, actually serves to give it more character, create a sense of history and make it more interesting to visit. Looking up at those great cracks in the masonry you feel as though you really are in a building that is more than 600 years old, a place where one of history's greatest conquerors once walked and worshipped.
That contrasts favourably with the many other ancient buildings in Central Asia which were restored during the Soviet era to a state of somewhat artificial perfection. They feel almost as though they were built only yesterday which, relatively speaking, they were.
For instance, the nearby Registan, once linked to the cathedral mosque by a covered arcade, has been almost completely restored and though it is - as Lonely Planet's Central Asia put it - "the centrepiece of the city and one of the most awesome single sights in central Asia," it doesn't actually generate much of a sense of history.
The awe, there, is rather at the magnificence of a complex which consists of three huge religious schools, gleaming with mosaics and blue-tiled domes, set around a sweeping, superbly proportioned square, dotted with gardens and fountains.
The square was intended by Timur to be the centrepiece of his city, set at the point where six avenues from the six fortified gates came together, and it must once have been a mass of stalls and traders, a hive of seething commercial activity.
But his grandson, the astronomer King Ulughbek, who ruled Samarkand for 40 years, changed the nature of the square when he built the first of the three great schools, now known as the Ulughbek Medressa, in 1420 and is even said to have taught mathematics there. He apparently had plans for the Registan to incorporate a mix of buildings including a mosque, a medressa, a caravanserai for visiting merchants and a bazaar, but his reign was cut short when he was assassinated and his ideas lapsed.
Instead, two hundred years later Emir Yalangtush, of the succeeding Shaybanid dynasty, built the Sher Dor (or Lion) Medressa opposite as an almost mirror image. It gets its name from the rather strange mosaic pictures of lions on the entrance which actually look very much like tigers.
A few decades on, the Shaybanids added the third, Tilla-Kari (or gold-covered) Medressa, named for the opulence of the decorations on the dome of its mosque, at the head of the square.
From the viewing point at its entrance the Registan is a beautiful sight, especially when the fountains are playing, and these days, far from its origins as a scene of noisy commercialism, it's more a place of quiet contemplation.
The old trading spirit does live on, however, behind the magnificent facades of the medressas. Some of the larger rooms now serve primarily as museums with displays of art or photos of how the place looked before it was restored. But everywhere there are women selling pieces of embroidery and jewellery or men offering paintings and small mosaic pictures. The dormitory cells where students once lived have now mostly been turned into small stalls. And the courtyard of the Sher Dor Medressa - which was undergoing further restoration during my visit - is often used for banquets.
But it's all a bit... pristine... lacking either the crumbling majesty of the cathedral mosque, the elegance of Timur's tombs - which are so superb that I've written about them separately - or the lively vitality found at the city's new main bazaar nearby.
Timur would doubtless be outraged at the decline of the city he poured so much wealth and energy into and especially at the fact that in 1930 it was displaced as Uzbekistan's capital by Tashkent.
But what he did achieve was to make Samarkand one of the glittering fabled cities of the world - with Atlantis and Eldorado - and alone among them Samarkand is real, it can be visited ... and it almost lives up to its magical fairytale reputation.
Getting there: Singapore Airlines operates 12 times a week between Auckland and Singapore and then onward to 62 destinations in 34 countries, including China.
Getting around: World Expeditions operates its Silk Road expedition from Beijing to Samarkand in April, May, August and September. Ring 0800 350 354.
Jim Eagles visited Samarkand with help from Singapore Airlines and World Expeditions.