A top priority for us was making sure to see Edinburgh Castle, one of the most popular sites in the city (and for good reason). Particularly if you’re traveling peak season, I recommend going early to beat the crowd and make sure you have plenty of time to explore. The castle opens at 9:30am; we went around 9:15 and there was already a large crowd, though the line went quickly. Tickets cost about 16 pounds apiece, which includes an optional guided tour, viewing of the royal Scottish jewels (lower your expectations if you’ve seen the jewels in London), and seeing a cannon dating back to 1861 fire at 1:00 to inform ships of the local time.