Mixing in porous media is relevant to a number of geophysical subsurface flows, such as water contamination, petroleum migration, sea ice formation and geological sequestration of carbon dioxide. In these processes, the fluid carries a dispersed phase (solute) that induces density differences within the fluid domain, resulting in convective motions driving the flow. The flow dynamics in these systems has a multiscale character: diffusion controls solute mixing at the scale of the pores, while large-scale convective structures drive the flow, further enhancing mixing. Therefore, an accurate description of the long-term flow dynamics requires to account for both pore-scale and large-scale effects. In this work, we present our recent findings and modelling strategies of convective porous media flows. We discuss simulations (namely pore-scale, Darcy-scale, and gravity currents) and experiments (Hele-Shaw and bead packs). Finally, we propose simple physical models to explain our findings and we discuss the limitations of the approaches proposed.