The obvious place to begin exploration is Stephansplatz, the pedestrianized central square dominated by the hoary Gothic Stephansdom (Mon–Sat 6am–10pm, Sun 7am–10pm, except during services; free, but entry fees to most sections, combined ticket €17.90). It’s worth paying to explore the interior more fully, with the highlights of the main section (English tours Mon-Sat 10.30am; €5.50) the Wiener Neustädter Altar, a late Gothic masterpiece, and the tomb of the Holy Roman Emperor Friedrich III. The catacombs (tours every 15–30min, Mon–Sat 10–11.30am & 1.30–4.30pm, Sun 1.30–4.30pm; €5.50) contain the entrails of illustrious Habsburgs housed in bronze caskets. Stellar views reward those climbing the 137m-high (343 steps) south spire; (daily 9am–5.30pm; €4.50). Lower, but with a lift, is the north tower (same hours; €5.50). The warren of alleyways north and east of Stephansdom preserves something of the medieval character of the city, although the architecture reflects centuries of continuous rebuilding.