No, it surrounds it.
The third ventricle
intermediate mass
The thalamus is situated at the top of the brain stem, connecting the brain to the spinal cord and vertebrates. The thalamus wraps around the third ventricle, making up the upper part of the ventricle wall.
The hypothalamus is a small mass below the thalamus and forms floor and part of the lateral walls of the third ventricle.
Thalamus
thalamus
The diencephalon consists of thalamus, hypothalamus, and epithalamus.
The thalamus and hypothalamus are regions of gray matter that form the lateral walls of the third ventricle in the brain. They are important for relaying sensory information and regulating various functions such as hormone secretion, sleep, and temperature control.
The narrow cavity along the midline superior to the hypothalamus and between the right and left halves of the thalamus is the third ventricle. It is one of the four interconnected ventricles within the brain that produce and store cerebrospinal fluid.
diencephalon
The 'Thalamus'
It is a median cleft between the two thalami, and is filled with cerebrospinal fluid. It is in the midline, between the left and right lateral ventricles. Running through the third ventricle is the Interthalamic adhesion, fibers which connect the two thalami.