This guide does not list individual places yet.
消防博物館
Three fire-fighting helicopters, ten trucks, and 3 floors of exhibitions. Very popular with kids, who can wear fire-fighting clothes and ride some of the helicopters and trucks.
花園神社
More remarkable for its location than its appearance, but it's a nice place to take a breather. There's often a flea market in the surrounding park on weekends.
新宿御苑
A large public garden, and one of the most popular places for viewing cherry blossoms in spring. It has Japanese, English and French gardens, as well as a Taiwanese teahouse and a greenhouse. The entrance fee often makes the park surprisingly uncrowded and peaceful. Admission ends 30 minutes before closing.
It is perfectly safe to walk around here during the day and marvel at the photo billboards of various male and female escorts on offer as well as the live gangster-types acting shady. While it probably shouldn't be done with children, for adults the result is far more "cultural interest" than sleaze.
新宿サザンテラス
The promenade next to the Southern Terrace exit offers a magnificent view of the Takashimaya department store and a bridge that offers the best spot for watching trains enter and exit. Starbucks, Shake Shack and other restaurants.
都庁 tochō
The two enormous buildings of this giant hive of bureaucracy are an Orwellian architectural masterpiece designed by noted architect Kenzo Tange. The main reasons to come here, though, are the twin observatories. At a height of 202 m on the 45th floor, they have some of the best views of Tokyo. The North Observatory is open daily from 09:30 to 23:00 (closed second and fourth Mondays of each month), while the South Observatory is open daily from 09:30 to 17:30 (until 23:00 on the days the North Observatory is closed; closed on the first and third Tuesdays of each month). Last entry is 30 minutes before closing.