Abstract: The flag variety $\mathcal{F}\ell_n$ is a smooth projective variety consisting of chains $(\{0\}\subset V_1\subset\cdots\subset V_n=\mathbb{C}^n)$ of subspaces of $\mathbb{C}^n$ with $\dim_{\mathbb{C}} V_i=i$. Then the standard action of $\mathbb{T}=(\mathbb{C}^\ast)^n$ on $\mathbb{C}^n$ induces a natural action of $\mathbb{T}$ on $\mathcal{F}\ell_n$. For $v$ and $w$ in the symmetric group $\mathfrak{S}_n$ with $v\leq w$ in Bruhat order, the Richardson variety $X^v_w$ is defined to be the intersection of the Schubert variety $X_w$ and the opposite Schubert variety $w_0X_{w_0v}$, and it is an irreducible $\mathbb{T}$-invariant subvariety of $\mathcal{F}\ell_n$. A point $x$ in $X^v_w$ is said to be generic if $(\overline{\mathbb{T}x})^\mathbb{T}=(X^v_w)^\mathbb{T}$. In this talk, we are interested in the $\mathbb{T}$-orbit closures in the flag variety which can appear as a generic $\mathbb{T}$-orbit closure in a Richardson variety. We discuss topology and combinatorics of such $\mathbb{T}$-orbit closures. This talk is based on joint work with Eunjeong Lee and Mikiya Masuda.