The top quark, discovered in 1995 by the CDF and D0 experiments at the Fermilab's Tevatron proton-antiproton collider, is the heaviest known elementary particle today. It has a life time shorter than the time for hadronisation, allowing its spin information to be accessed from its decay products. These features make the top quark a special particle to study. In this presentation, we focused on recent results from the ATLAS experiment in the top sector. In particular, we presented a new result on QCD colour-flow studies in top quark decays, a new measurement of spin correlations in top-antitop quark events, and new limits on the production of events with four top quarks. All results use a data sample of 36 fb$^{-1}$ of integrated luminosity, recorded with the ATLAS detector at $\sqrt{s}=13$ TeV collision energy.