Utrecht University flourished in the seventeenth century, and contributed significantly to the Dutch Golden Age, despite competition with the older universities, such as Leiden (1575) and Groningen (1614). Leiden, in particular, proved a strong competitor and made further improvement necessary; a rivalry that persists to this day. A botanical garden was built on the grounds of the present Sonnenborgh Observatory, and three years later the Smeetoren added an astronomical observatory. The university attracted many students from abroad (especially from Germany, England and Scotland). They witnessed the intellectual and theological battle fought between proponents of the new philosophy (René Descartes lived for a few years in Utrecht) and proponents of the strict Reformed theologian Voetius. They also witnessed the teachings of renowned Dutch jurist, Johannes Voet, a university alumnus and professor of law, whose works remain highly authoritative in modern Roman-Dutch law.