From CloudModding OoT Wiki
Actor 0x009B
Version VRom VRam Size
Debug 00D4D530 00D4DC20 {{{ram-start}}} {{{ram-end}}} 6F0
NTSC 1.0 00CF70A0 00CF7710 {{{ram-start}}} {{{ram-end}}} 670
PAL MQ 00CF8180 00CF87F0 {{{ram-start}}} {{{ram-end}}} 670

ovl_Door_Ana is the actor used for the secret Grottos that can be found around Hyrule.

General Notes

Grottos are not as straightforward as they appear. Whenever you touch a grotto, Link's x,y,z coordinates, the the current entrance index, and the current room number are saved to a specific spot in ram. This makes it possible to reuse the same grotto in multiple scenes, and be able to return to the correct location.

Additionally, there exists a "generic" grotto contains a single chest. The contents of this chest and the chest's bound switch flag can be set via the grotto's initialization variable. This part of the initialization variable is saved in a specific part of memory, which is then read by an instance of the ovl_En_Torch (0181, Grotto Treasure Chest) actor, which uses the data to spawn instance of ovl_En_Box (000A, Chest)

When you die in a grotto, you spawn somewhere weird, and i forget how this works.

When you cast Farore's Wind in a grotto (probably checks scenes 60 and 62), the return point information is set based on Link's previous "checkpoint" before entering the grotto.

NTSC 1.0 notes

9B code (file at 2690)

2974 <- return point after storing grotto coords
29A0 = Store lower byte of actor varible (11B967)
29A4 = Load Z rotation v0
29A8 = Increment 1
29B4 = Load Entrance Index to t5
29D0 = Store Entrance Index in next entrance (1DA2BA)