Realm 1

REALM 1, aka FAMILIAR RUINS is the 1st realm in Tubular Rift. It was first released same as in the release of the game itself.

Beginner Towers:
ToT - Tower of Teaching

ToZ - Tower of Zen

Intermediate Towers:
ToSC - Tower of Slight Concern

ToSE - Tower of Smooth Edges

Advanced Towers:
ToW - Tower of Wedges

ToUM - Tower of Unique Mechanics

Mentally Dangerous Towers:
ToEW - Tower of Endless Wraparounds

ToU - Tower of Umbrage ( It was meant to be for ToVF but was changed )

SC Tower:
VV - Violet Violence

Citadel:
CoP - Citadel of Pipes

Spire:
SoCT - Spire of Casual Traversing

Removed:
ToCE - Tower of Close Endarment

TT - THE TOILET (Was an event tower - now discoverable in The Lab's basement)

ToAF - Tower of Aesthetic Fantasies

ToTD - Tower of Treacherous Dying (Was stated as CLOSED FOR REVAMP, but instead was replaced by Violet Violence)

Events:
SoC - Spire of Celebration (100k Event Spire)

Sky Lobby
Go past Mentally Dangerous Tower and look for a tower portal that says "Sky Lobby"

FUN FACT: For some time, the Sky Lobby was replaced with THE TOILET.

SoCT Guide
Go past Mentally Dangerous Towers to near the sky lobby. Then the spire will be inside a ruined tower alike to FoRD (Fortress of Rising Difficulty).

ToTD / VV Guide
Go near the sky lobby and look around for a dark passage way inside a rock. Do the parkour, and Tower of Treacherous Dying (now Violet Violence) will be right infront of you.

CoP Guide
Go to the right of the beginner towers and climb the rocks, then hop into the pipe and Citadel of Pipes will be infront of you.

SoC Guide
Go to where ToTF (Tower of Total Fury)'s ruins are and touch the cake - there you'll be sent without the showcase of the portal.

Trivia

 * The Realm's name is similar to one of the classic official FE2 maps.