Castlevania 64/Forest of Silence

Sealed gate
From the start, walk to a fork. Trees fall on your left, but there are torches beyond them: take that direction and grab the items. It's a dead end, so backtrack and continue in the other direction. You will see a dead villager, and suddenly the earth will start shaking and skeletons will start attacking you. Skeletons keep spawning until you get close to the gate. Break the seal by hitting it, and the gate will open to reveal the first of three sub-bosses.

Sub-BOSS: Giant Skeleton, round 1
The giant skeleton primarily raises more small skeletons from the ground. Periodically, it also swing its club. If you're close enought to it and time your jump, it can smash its own minions. When its life bar (lower-right corner of the screen) gets low, it will move in the area beyond the open gate. Before getting completely defeated, it will escape jumping in the river.

First switch and gate
Jump across the river and continue straight until you get to the next gate. There's a White Crystal (save point) near there, so save your game.

The gate is obviously closed, so you have to look for a way to open it. Take the other fork (without crossing the river again) and you'll get to two sepulchres. There are torches with items both inside and on top of them. In order to jump to the top of the sepulchres, there are two steps on their left that can help. Continue and cross the river again, and activate the switch.

Sub-BOSS: Were-tiger
As you activate the switch, the second sub-boss attacks, surrounded by a swarm of skeletons. Keep a safe distance from the were-tiger, because if he grabs you he will slam you to the ground like a fresh-caught octopus.

Second switch and gate
Backtrack to the now open gate and save. Blue bomb skeletons start spawning now, mixed with the regular ones. There is a sepulchre and a statue in this next area. Inspect the statue and open the coffins to get items. Continue to the fork; the sign points to the next locked gate, but also to the White Crystal (save point). When you're done saving, take the other direction. Cross the river to get to the switch. Luckily, no were-tiger attacks you, but unlickily the platforms drop, so you have to fight against the camera instead!

Special Item
Walk past the open gate, fight the skeletons, open coffins in the mausolea, locate the gate, continue towards the river crossing. When you're on the pillar top, look at the floating platform with a torch. Can you get there? Yes, and easily, too: there's an invisible bridge, and you can easily walk on it. The torch contains the Special Item 1, that unlocks the Hard Mode once you clear the game normally.

Third switch and gate
Cross the river and walk under an open arch. Locate the werewolf in the distance, to the left of the statue. When you get closer, he will charge at you. He's very fast, so attack him with a ranged weapon (possibly a cross) even before he gets close. It's a tough opponent, but he always drops some roast when he's defeated. Is it roasted wolf?

Examine the statue and the coffins, then walk on, get to the bottom of the river and operate the switch. Backtrack to the statue and sepulchre, but the gate is still closed. How come? It is the wrong gate! Anyway, there's a White Crystal (save point) next to it. Backtrack more to the area with the three mausolea, and walk under the open gate there.

Fourth switch and gate
The fourth switch is just past this newly-open gate. Now backtrack again to the area with the last gate, that is finally open.

BOSS: Giant Skeleton
Cross this open area, but when you get close to the river, the giant skeleton will climb out of it. Two hellriders, i.e. skeletons on anachronistic motorcycles, flank the giant. Just hit the bikers once or twice to defeat them. The giant skeleton follows a similar strategy as before. As it weakens, he will first lose an arm, then the legs. When he loses the legs, he cannot summons skeleton minions anymore: the worst it through!