The Legend of Zelda: Breath of the Wild does this sneaky thing where stronger enemies will populate the world as you progress deeper into the game. Enemy strength is indicated by their color. For example, in my completed save, I'm seeing white bokoblins show up in previously beginner-friendly areas, and they're significantly stronger than the usual brown ones.
If you ever want to take on a slew of enemies that's scaled to your level (and collect some rare weapons while you're at it), there's a coliseum challenge waiting for you.
Zelda: Breath of the Wild coliseum location and guide
The coliseum is super easy to find; you might accidentally wind up there near the beginning of the game if you aren't careful. It's immediately to the north of the Great Plateau starting area and east of the Outskirt Stable. The easiest way to approach it if you don't have a lot of stamina for climbing or the Revali's Gale power is from the north. There's a ton of Ganon's black malice ooze around the coliseum, but the north entrance provides a clear path inside.
Waiting for you on the ground floor is the toughest enemy in the entire place, our old friend Lynel. You can try running past him onto the upper levels if you want to avoid him, but be warned that he'll rain deadly arrows on you if you do that. Since you're here to fight, you might as well fight.
The whole gimmick to this area is that it's full of the most powerful enemies relative to where you are in the game, and each of them is wielding rare weapons for you to take once you've disposed of them. In my game, the Lynel at the entrance is the silver-maned variety, which is the strongest in the game. All of the bokoblins and lizalfos on the upper levels are more powerful than the garden variety ones you'll see closer to the beginning of the game.
Most importantly, every single enemy has some kind of elemental weapon. Flameblades, thunderblades and frostspears are plentiful in the coliseum. This is basically a farming ground for elemental weapons and monster parts. If you want to buy the Dark Link outfit, the coliseum is a decent place to start. There isn't anything here besides combat and loot, though, so if you're more interested in exploration and puzzles, maybe go somewhere else.
More Zelda: Breath of the Wild tips, tricks and guides
Find out all there is to know about Zelda: Breath of the Wild, including what to expect from the Wii U version, how to preserve your items, how to beat bosses like the Stone Talus, Lynel, the Guardians and the Hinox, the best recipes for Link, how to take on the game's shrines and our coverage of the game's outfits, like the Climbing Set, the two sets of heat resistance armor you can find and how to dress Link in the classic green tunic. You'll also want to find out where all the great fairies in the game are, all available stables, how to use amiibo with your version of Zelda and how to increase your health, stamina and weapon slots.