Castlevania 64/Tunnel and Underground Waterway

The rock crusher
To pass the first rock crusher, run under it. To pass the second rock crusher, get near, let both blades fall, then jump over them.

Get on the lift and descend to the lower level.

The underground river
As in the Forest of Silence, the river water is poisoned: falling in it means instant death.

After you cross the river once, there are a few forks. The quick path is to always take the left fork. The forks to the right get you to some items. Inspect all signs to get an item from one of them.

Get on the lift and ascend to the upper level.

The gondolas
Another area with several forks. The quick path is to take the right fork until you get to a door. Backtrack from the door, run straight until you get to a red gondola. There's a white save crystal on the way there, right after the rock crusher.

Get on the red gondola and get off at the first opportunity. A sign there instructs you to wait for the blue gondola. Many evil ghosts will keep you company, and a yellow log will try to trip you right before the blue gondola arrives. Get on the blue gondola and get off at its station. There is another white save crystal near the lift.

Get on the lift and descend to the lower level.

The straight maze
After the pit, the quick path is to go just straight until you get to a Sun door. There are many forks, but ignore them: they take lots of time and the reward is limited. Open the Sun door to meet Rosa the kind vampire. There's no boss fight, just a cutscene.

The first switch
The beginning of this stage is extremely tricky. First the floor will crumble under your feet, then you have to jump and grab a narrow ledge to get past the pit.

Soon, you'll be attacked by a group of three lizard men. Two will engage you in close combat, the third one guards the first switch.

After the lizard men are defeated, step on the switch to stop a waterfall of poisoned water.

The second switch
Get past the dry waterfall, but beware of a lizard man hiding behind a pillar of the bridge. Run straight to the end of the visible tunnel to get to a white save crystal.

Backtrack and get in the side tunnel, but beware of the crumbling floor. After the tunnel there is a wall with a narrow aperture below. Carrie can crouch and crawl under it to get some items.

When you get to a larger hall, jump from pillar to pillar across the poisoned water. You'll evetually reach the second switch. Step on it to open a portcullis.

The third switch
Backtrack across the pillars and run to another tunnel: it leads to the now open portcullis. In that room you can find the third switch. Step on it to stop another waterfall.

Backtrack to the large hall and walk to the far corner, past the dry waterfall. Open the Sun door to meet Actrise the witch. There's no boss fight, just a cutscene.