Question

Nothing beside remains.round the decay
Of that colossal wreck,boundless and bare
The lone and level sands stretch far away
1. What does Colossal wreck refer to

Answer 1

'Colossal' means very huge or incredibly big.

Here, colossal wreck refers to the ruins of Ozymandias' statue.  His statue couldn't survive the ravages of time and ultimately, got destroyed.

His statue is considered insignificant and is an example how vanity and arrogance never lasts.

Hope it helped!
NISHTHA.

Answer 2

Simply ozymandias statue in the Mondale of the lonely sandy desert
With its broken visage