Café De Werf is the kind of traditional Belgian brown café that Leuven used to have many more of — a dim, woody interior, wooden tables, and a blackboard listing the beers on tap alongside a short food menu of soups and cheese plates. It sits a short distance from the Oude Markt's main concentration of bars, which means it tends to attract a slightly more mixed crowd: students alongside regulars who have been drinking here for decades.
The beer selection focuses on Belgian ales, with rotating taps featuring regional brewers alongside the omnipresent Stella (which is, of course, brewed in Leuven). It's open from mid-afternoon until late and is at its best in the evening, when the combination of low lighting, comfortable noise level, and genuinely good beer makes it an easy place to spend two hours without noticing.