What it is
The Financial District (FiDi) occupies the southern tip of Manhattan, the area settled first by the Dutch in the 1620s and still the densest concentration of 19th and early 20th century commercial architecture in the city. The financial institutions that gave it its name have largely relocated to Midtown or dispersed globally — the neighborhood's identity is more complex now than the name suggests.
The 9/11 Memorial and Museum
The twin reflecting pools — set in the exact footprints of the original towers, water sheeting continuously down their sides — are among the most affecting public memorials in any city in the world. The underground museum is extensive, harrowing, and worth planning significant time for. Book timed tickets in advance; the grounds are free, the museum is ticketed.
The architecture
Wall Street's canyon of early 20th century bank buildings — some of the finest Beaux-Arts commercial architecture in the country — is genuinely worth a slow walk rather than a hurried transit. Trinity Church (1846) at the head of Wall Street is an anomaly: a Gothic Revival church surrounded by skyscrapers, with Alexander Hamilton buried in its churchyard. The Woolworth Building (1913), briefly the world's tallest, is visible from most of Lower Manhattan and still striking.
The Oculus and Fulton Center
The Oculus — the World Trade Center transit hub designed by Santiago Calatrava — is a massive white ribbed structure that functions as both a PATH station and a shopping mall. Architecturally striking, practically useful, and worth seeing even if you're not taking a train.
Getting around and eating
FiDi is well-served by multiple subway lines (1/2/3, 4/5, A/C/J/Z). Restaurants and cafés close early or go service-industry-only on weekends when the office population empties out — but those same weekends are the best time to visit, when the streets are unusually quiet for Manhattan.