Complex sentence: The staircase was badly damaged by a fire that swept the palace in 1837, but Nicholas I ordered the architect in charge of reconstruction, Vasily Stasov, to restore the staircase using Francesco Bartolomeo Rastrelli's original plans.
Split into simpler sentences: The staircase was badly damaged by a fire that swept the palace in 1837. But Nicholas I ordered the architect in charge of reconstruction, Vasily Stasov, to restore the staircase using Francesco Bartolomeo Rastrelli's original plans.