The wide Danube was always fordable at this point because of a small number of islands in the middle of the river. The city has marked topographical contrasts: Buda is built on the higher river terraces and hills of the western side, while the considerably larger Pest spreads out on a flat and featureless sand plain on the river's opposite bank. Pest's terrain rises with a slight eastward gradient, so the easternmost parts of the city lie at the same altitude as Buda's smallest hills, notably Gellért Hill and Castle Hill.