Yeah, my first answer to "what city in Texas is best to visit" is Austin. But a big part of that is the music, and most of that is in the evenings, missed by someone coming in for a day trip MR. And much of the rest of what appeals to me in Austin is outdoors, from Town Lake and the park, to the bar patios on Rainey St, to the bike share system & bikeability of downtown. So for a summer afternoon, when it may be 100 in the shade, maybe not so much.