What's a grand Android app for using maps when I'm properly off-grid and can't rely on data?

Honestly, Avenza Maps has saved me countless times on my travels. It's brilliant for when you're trekking in the Himalayas or exploring the backroads of Ireland, and your data connection decides to take a holiday. You just download the maps you need beforehand – I've downloaded maps for all of Southeast Asia at one point – and then you can use them completely offline. It doesn't eat up your roaming data, which is a massive bonus. I remember being lost in rural Vietnam, and Avenza Maps got me back on track. It's a proper useful app, and I wouldn't go anywhere without it now. It's especially good if you're doing any hiking; you can find maps that show all the trails. Plus, it works perfectly in rural Thailand where finding wifi is like finding a unicorn. Absolute lifesaver!