Let $X_{t}$ be a generic, nonsingular quintic in $\mathbb{CP}^{4}$ near the large complex structure limit. Then Ruan’s construction yields a Lagrangian fibration $f:X_{t}\rightarrow{\mathcal{S}}^{3}$ with the following properties:

• (i)

  $f$ is a piecewise smooth map.

• (ii)

  The set of singular points in $X_{t}$ of singular fibres of $f$ is a holomorphic curve in $X_{t}$.

• (iii)

  The set $\Delta=\{b\in B:f^{-1}(b)$ is singular$\}$ is a $2$-manifold with boundary in ${\mathcal{S}}^{3}$. It splits naturally into a disjoint union $\Delta=\Delta_{0}\cup\Delta_{1}\cup\Delta_{2}$, where $\Delta_{2}$ is the $2$-dimensional interior of $\Delta$, and $\Delta_{1}$ is a finite set of open intervals on the boundary of $\Delta$, and $\Delta_{0}$ is a finite set.

• (iv)

  If $b\in{\mathcal{S}}^{3}\setminus\Delta$ then $f^{-1}(b)$ is diffeomorphic to $T^{3}$.

• (v)

  If $b\in\Delta_{2}$ then $f^{-1}(b)$ is a $T^{3}$ with two isotopic circles collapsed to two singular points.

• (vi)

  If $b\in\Delta_{1}$ then $f^{-1}(b)$ is a $T^{3}$ with one circle collapsed to one singular point.

• (vii)

  If $b\in\Delta_{0}$ then $f^{-1}(b)$ is a $T^{3}$ with one $T^{2}$ collapsed to one singular point.