AbstractLet X and Y be compacta. A map f:X→Y is said to satisfy Bula's property if there exist disjoint closed subsets F0 and F1 of X such that f(F0)=f(F1)=Y. It is well known that a surjective open map f:X→Y with infinite fibers satisfies Bula's property provided Y is finite-dimensional. In 1990 Dranishnikov constructed an open surjective map of infinite-dimensional compacta with fibers homeomorphic to a Cantor set which does not satisfy Bula's property. We construct another type of maps, namely, monotone open maps on n-manifolds, n≥3 with nontrivial fibers which do not have Bula's property. Our construction essentially applies Brown's theorem (1958) on a continuous decomposition of Rn\{0} into hereditarily indecomposable continua separati...