In 630 AD, Chinese pilgrim Xuan Zang wrote of Bamiyan in Afghanistan"There is a stone image of a standing Buddha carved into the mountainside northeast of the palace. Shining in gold, and adorned with jewelry, the statue stands about 45 metres tall. To the east of the temple, stands another statue of a 30-metre-tall Buddha made with brass."
Of course he was describing the famous Bamiyan Buddhas which had been carved directly from the surrounding sandstone cliffs and which were tragically destroyed by braindead Taliban in 2001. The Buddhas were, in fact, 55 and 38 metres tall respectively but pretty good guesses nonetheless. It's with this sense of the commentator's accuracy that you need to assess the other thing he wrote:
"Inside a Buddhist temple located about 10 kilometres from the palace, there is a statue of Buddha in a state of passing into nirvana. The image of the supine Buddha is as long as 300 metres."
Reclining buddhas remain a common feature of Buddhist temples around the world but this one would have been extraordinarily long, the equivalent of the Eiffel tower placed on its side. It's shoulder would have been about 25 metres high.
Remarkably, this structure has never been found however Xuan Zang is considered such a reliable witness that most archaeologists accept that it must have really existed. Now a team of French archaeologists under the direction of Zemaryali Tarzi of Strasbourg University, who have been searching for it in earnest for two years, are claiming that they may have discovered part of the foot of the statue.