The natural starting point in St. Pölten is Rathausplatz (Town Hall Square), the long Baroque square at the heart of the old town. Pastel-coloured facades line all four sides, the town's tourist office stands at one end, and pavement cafés spill out into the square in warm weather. The square is dominated by the Town Hall (Rathaus) on its southern side, which combines a Renaissance tower with a Baroque facade from 1727 by Joseph Munggenast and a small set of Gothic niches that survive from earlier centuries. At the northern end of the square stands the Franciscan Church (Franziskanerkirche), completed in 1770, with a tall Baroque altar set against side-altar paintings by the eighteenth-century master Kremser Schmidt. The square has been the civic heart of St. Pölten for centuries and remains the most natural place to begin a walking tour of the centre. From here a short walk along the pedestrianised Wiener Straße brings you to the neighbouring Domplatz, the Cathedral Square, where a weekly market has been held on Thursdays and Saturdays since 1876.

The St. Pölten Cathedral (Dom zu St. Pölten) is one of the great architectural surprises of the city. Its plain Romanesque exterior gives little away, with a single surviving onion-domed south tower and twelfth-century walls largely unchanged on the outside. Step through the western door, however, and the interior opens out into one of the most richly decorated Baroque churches in Lower Austria. The origins of the building lie around the year 790, when a Benedictine monastery was founded on this site. After several rebuildings, the most decisive transformation came in the early eighteenth century under Provost Johann Michael Führer, who brought the leading Baroque artists of the Habsburg lands to St. Pölten. Architects Jakob Prandtauer and Joseph Munggenast reshaped the interior, while ceiling frescoes by Thomas Friedrich Gedon and Daniel Gran, side altars and paintings by Gran, and sculptures by Jakob Christoph Schletterer transformed the inside of the building into a high-Baroque sacred space of giant pilasters, barrel vaults, and gilded woodwork. Since 1785 the building has served as the cathedral of the Diocese of St. Pölten, and a small Romanesque rosary chapel preserves elements of the early medieval church beneath all the later splendour.

A short walk east of the old town lies the Cultural District (Kulturbezirk), built from the mid-1990s onwards when St. Pölten became the capital of Lower Austria. The district is the city's modern counterpart to its Baroque centre, a planned ensemble of administrative and cultural buildings designed by leading Austrian architects including Hans Hollein. At its heart stands the Lower Austria Museum (Museum Niederösterreich), set in a striking modern building by Hollein and combining two distinct museums under one roof. The House of Nature (Haus für Natur) presents the landscapes of Lower Austria from the high mountains down to the Danube basin and into underground show caves, with more than 40 live native animal species kept in aquariums, terrariums, and a formicarium, including green lizards, tree frogs, catfish, and a pair of sturgeon. The House of History (Haus der Geschichte), opened in 2017 over a total area of 3,000 square metres, traces the development of Lower Austria, Austria, and Central Europe through some 2,000 objects and a strong focus on the twentieth century. The same complex also includes the Festspielhaus St. Pölten, one of the leading centres for dance and music in Austria.

The single most distinctive landmark of the Cultural District is the Sound Tower (Klangturm), a 77-metre tower designed by the architect Ernst Hoffmann and opened in 1997 alongside the new capital. The building rises on a footprint of just fifteen by fifteen metres, built from 650 tonnes of steel and around 1,000 square metres of glass, and despite its size appears strikingly light and transparent against the sky. A panoramic lift, or 280 steps for the ambitious, leads to a viewing platform at a height of 47 metres, from which the whole of St. Pölten, the Cultural District, and the surrounding hills of the Mostviertel unfold. The tower's name comes from the sound-art installations inside, which present a changing annual programme of work at the intersection of visual art, media art, and music, in keeping with the architect's description of the building as a symbol of imagination at the heart of the administration. Access to both the viewing platform and the installations is free of charge, which makes the Klangturm one of the easiest and most rewarding stops in the city for a sweeping overview before or after exploring on foot.

St. Pölten's main railway station sits a short walk or bike ride from the centre of the old town, with Rathausplatz, Domplatz, and the Franciscan Church all reachable on foot in around ten minutes along flat, pedestrian-friendly streets. The Cultural District, including the Lower Austria Museum and the Klangturm, lies a fifteen-minute walk east of the station and is also served by the LUP city bus. The compact scale of both the historic centre and the Cultural District means most travellers explore on foot once they arrive. Cycling infrastructure in and around the city is good, and bike racks are available at the station for shorter stops. For onward travel, the same station connects back toward Krems an der Donau and the wider Danube region, as well as east toward Vienna and west toward Linz, so St. Pölten works equally well as a half-day excursion or as an overnight detour from the EuroVelo 6.