  We study cells in generalised Bott-Samelson varieties for type C. These cells
are parametrised by certain galleries in the affine building. We define a set
of readable galleries - we show that the closure in the affine Grassmannian
associated to a gallery in this set is an MV cycle. This then defines a map
from the set of readable galeries to the set of MV cycles, which we show to be
a morphism of crystals. We further compute the fibres of this map in terms of
the Littelmann path model.
