Many years ago, young men disappeared under the streets of Portland. They were hidden in tunnels and forced to work on ships. Explore a hidden city, a floating town, a city on ice, a city that is sinking, one with many forgotten tunnels, and a military base inside a mountain. Learn about these fascinating places.

Dark Tunnels is one of 6 books in a set called City Secrets, which is part of the Sound Out Phonics Based Chapter Books series. City Secrets (Sound Out Levels 5 and 6) focus on the following skills: contractions, one-syllable spelling patterns, tense endings, word endings, compound words, prefixes and suffixes, and simple two-syllable words. Readers will not be able to tell that each book is written using controlled vocabulary.