For a short “day trip” from Tokyo, hiking Mount Takao would be hard to beat. Taking the express train from Shinjuku station, you’ll be at the base of the mountain in less than 1 hour. Once there, you’ll find it very hard to believe that you’re so close to one of the biggest cities in the world. The beauty of the area is amazing. The air is clean and it’s incredibly QUIET.
Most of the tourist guides say to take route #1 to the top OR pay to ride the train and/or chairlift. I think route #6 is the best. Great views, less people AND it’s not nearly as steep. There are places to stop with benches to sit on at many places on the way up too.
Once on top, you’ll be treated to some amazing views. Then take the #1 trail back down the hill. It’s got a really wide, well paved track, so footing is easier than on #6. Something to consider if it’s rained recently too. Be sure to stop at the large temple on the way down. You may even encounter monks chanting in the main building. Please don’t take their picture or enter the room while they’re praying.
At the bottom there are a few restaurants, in case you want to fill your belly before heading back to town. All told, you can do the entire route at a moderate pace in about 4 hours.