Leave Richmond around 5:30 AM for the roughly 3–3½-hour drive to San Marcos, taking I-10 W, TX-130 S, and I-35 S. TX-130 is a toll road, so make sure your rental car or vehicle is set up for toll billing. The early departure is worthwhile: traffic is usually lighter, and you should reach San Marcos Premium Outlets near opening, when parking and popular stores are easiest. Check the center’s Sunday hours before leaving, as individual stores may vary.
Plan on three to four hours at San Marcos Premium Outlets, one of the largest outlet centers in the country. Wear comfortable shoes—the complex is spread out—and keep purchases in the car only if you can place them out of sight; otherwise, carry them with you. Around 12:30 PM, have lunch at Saltgrass Steak House near the outlet area. Expect approximately $20–35 per person for a steak, salad, or Texas-style entrée. Keep lunch fairly efficient because the afternoon’s timed cave visit is the day’s non-negotiable booking.
After lunch, drive about 35–45 minutes north via I-35 to Natural Bridge Caverns near north San Antonio. Reserve a timed guided cave tour in advance; admission commonly runs about $30–45 per adult depending on the tour and date, with additional charges for surface attractions. Allow 2½–3 hours, including check-in, the walk to the entrance, and the underground tour. The caverns are cool and damp year-round, while the surface can be hot in September, so bring water and wear sturdy, closed-toe shoes. If your tour is around 1:45–2:00 PM, you can enjoy one or two surface attractions afterward, but avoid adding too much if you want a comfortable drive home.
Leave Natural Bridge Caverns around 4:30–5:00 PM, using I-35 N toward Austin, then TX-130 N and I-10 E back to Richmond. The return generally takes about 3–3½ hours, though Sunday evening traffic near Austin and Houston can add time. Plan a quick rest or dinner stop along the route rather than trying to fit in another attraction; after outlet shopping and a cave tour, this is already a full day.
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