abstract: Matroids over rings were introduced by Luca Moci and the speaker as a common generalisation of valuated matroids and arithmetic matroids. This talk reports on a continuation of that work. After introducing matroids over rings and their principal known manifestations, we fully explain the structure of matroids over valuation rings. This leads to a cryptomorphic characterisation in terms of polytopes, and a construction of their parameter space with a tropical Schubert calculus flavour. A few yet-unreconciled clues hint at the existence of a Coxeter generalisation.